I think that one is okay. It's on the order of fish and fishes.
With fish, the plural is "fish" when speaking of many fish of the same kind. When speaking of different species collectively, it's "fishes."
The parallel is that when speaking of different currencies or monetary units collectively, it's "monies," but when speaking of the sum in your pocket, it's still "money" even if it is made up of coins and paper.
Back to money, when counting out change, you would still say, "eight, nine, ten, and ten is twenty", not "...and ten are twenty" as in several coins and paper; you would say "is" because it's a singular concept of one sum total number.
-PJ
I also think of “monies” as coming from separate revenue accounts or budgets.