Pennies (2 decimals) is not fine enough. Exchanges and other financial services use 4, 6, or maybe even 8 decimals. With 6 decimals, a few trillion is the limit

Pennies (2 decimals) is not fine enough. Exchanges and other financial services use 4, 6, or maybe even 8 decimals. With 6 decimals, a few trillion is the limit. If you implement multiplication and division with integer arithmetic, you need the additional decimals to keep the error small. See https://en.wikipedia.org/wiki/Salami_slicing https://en.wikipedia.org/wiki/Salami_slicing