Nitpick: Most finanical packages work on 1/100ths of a cent, not on cents. Otherwise yes, everything money-related should use fixed point and be really careful about over/underflow.
Although one fairly well-known package, produced by a place I once worked briefly, which (when I worked there) internally used doubles for all money values, wrapped in a class that re-rounded the results every so often. No, really.
Although one fairly well-known package, produced by a place I once worked briefly, which (when I worked there) internally used doubles for all money values, wrapped in a class that re-rounded the results every so often. No, really.