Abivia Money supports BCMath with rounding for currency calculations.

Version 1.2.0 updates:

• Money::comp() now treats a missing argument as a zero value.
• Added Money::quantum($scale) which returns a Money object containing the smallest unit for that scale (so quantum(2) returns 0.01).
• __get() now formally returns a mixed type (thanks @JaberWiki).

https://github.com/abivia/money