Currently all currencies on actor sheets are limited to integers, but there are some systems that use fractions of a denomination (such as the credits in Dark Matter from Mage Hand Press). The system should have support for this. The simplest way would be to just remove integer: true from the CurrencyTemplate data module, but it might be helpful to also allow specific denominations to specify whether they support decimals or not. Then Dark Matter could allow decimal credits while standard DnD5e would still require whole-number gold pieces.