probably none. To handle currency correctly you have to handle rounding to the nearest penny correctly. Computers absolutely SUCK at this, in general. So you need a Decimal library, that can handle decimal numbers. Integers ARE NOT DECIMAL.

IBM has had a solution for a long time: http://speleotrove.com/decimal/

Python uses it: https://docs.python.org/3.5/library/decimal.html

Get a proper decimal library, and then you can devote brain cells to actual problems. The IBM link above includes links to libraries that do it right.