Companies have various legal entities which operates in different currencies.

It would be ideal to configure the decimal places as per the legal entity.

Currently there is no out of the box setup available to do this

The below blog discusses the issue in details

https://community.dynamics.com/ax/f/microsoft-dynamics-ax-forum/236343/currency-3-decimal-is-required-for-one-entity-and-2-decimal-is-required-for-other-entity-in-ax-2012/651842