Here is the same paragraph in Russian:
Произошло подсчитывание, пересыпаемое шуточками и прибаутками Коровьева, вроде «денежка счет любит», «свой глазок — смотрок» и прочего такого же."
I initially presumed these were Russian sayings of some sort
They are but, as you said - they are of the sort that is not expected to be found in "A Collection of Russian Sayings" type of books (for English speakers). Probably not considered important enough, so this is why you "can't find any references to them as such".
I presume, in any language there are such "quips" that all the natives immediately recognise, use and understand but they can't be found in any dictionaries. For example, in English people say "Better out than in" (often used when someone accidentally burps or pukes). Well, Koroviev's utterances are of that sort.
As to the meanings of those utterances - the translation is correct. Albeit, it does not convey the subtle nuances of the language as happens with most (if not all) translations.
The use of "денежка" instead of "деньги", "глазок" instead of "глаз": diminutive suffixes is a feature of Russian, not present in English. Well, the use of "Johnny" instead of "John", "doggie" for "dog", and the like is close, but in Russian this "language tool" is more flexible and more widely used to convey the subtleties. Those suffixes give a Russian native reader an additional sense of "non-seriousness" of Koroviev: he acts and talks in a deliberately jocular way, even overplays (again - deliberately), because his ultimate goal is to con Nikanor Ivanovich into making a deal with him, the deal that smells 'dodgy'.
Judging from this excerpt, the translator did a fairly good job: «свой глазок — смотрок» rhymes in Russian and the translator put it as ‘Your own eye won’t lie’, which also rhymes. Not bad at all.
and what are they supposed to imply in the context of this scene
Not easy to explain because, being a native Russian, I just "know" but never actually needed to explain this to an English native. I'll give it a try, though. So, these ‘Cash loves counting’, ‘Your own eye won’t lie’ are being said during the process of "counting-up" the cash that Koroviev just handed to Nikanor Ivanovich and, in this context and situation, the expressions have an implication, which I can only put as "You'd better count the money carefully. Never trust anyone when it comes to money, right? And you, Nikanor Ivanovich, know this only too well - you cheated people at every opportunity yourself when it came to money", etc.
In other words, Koroviev uses the expressions that Nikanor Ivanovich himself has been using as his sacred principles all his life. (For those not familiar with the book - Koroviev is not a human, he accompanies Satan (Woland), so he can "read" humans inside out.)
A few more details came to mind, maybe this is what the OP wanted in the first place:
"денежка счет любит" ("cash loves counting") - in various forms this expression is still widely used in modern Russian. The refined meaning is "Money is something you have to be accurate with, you need to count it to make sure everything is in order". Actually, having read it again - "cash loves counting" I would change to "cash loves being counted", so maybe not such a good translation after all.
«свой глазок — смотрок» ("Your own eye won’t lie") - although easily understandable by natives, the expression is hardly ever used these days. Very colloquial, lots of similar (in style) expressions can be found in Russian traditional fairy tales and proverbs. "Смотрок" is a made up word, you won't find it in a dictionary, derived from the verb "смотреть" ("to look, to watch") in a form rhyming with "глазок" (diminutive form of "an eye"). The meaning is something like "You can only trust what you can see with your own eye(s)". There might have been a second part of this expression (typical for Russian sayings), which is omitted in this text and I'm not aware of it.
Apparently, the proverb in its full form can be found in "В.И. Даль. Пословицы русского народа" (Vladimir Dahl "Proverbs of the Russian people"): "Свой глазок - смотрок. Не верою, а видением.", as well as in the "Большой русско-английский фразеологический словарь" ("The large Russian-English Phraseology Dictionary"), where one can also find the same quote from Bulgakov in a slightly different translation:
"...[Коровьев] выложил председателю пять новеньких банковских пачек.
Произошло подсчитывание, пересыпаемое шуточками и прибаутками
Коровьева, вроде "денежка счёт любит", "свой глазок - смотрок" и
прочего такого же (Булгаков 9) Не [Koroviev] stacked five bundles of
new bank notes before the chairman. There was a careful count,
interspersed with Koroviev's little quips and pleasantries, such as
"money loves to be counted," "your own eye is the best spy," and so on
in the same vein (9a)."
The second part of the proverb ("Не верою, а видением.") means "Seeing is believing".