Not all, many situations make use of prices and calculations in the fractions of a cent. For example forex trading, or even gas stations.

Generally decicents (10 decicents = 1 cent) makes all normal currency calculations much easier/reliable. If you need lower resolution use millicents or microcents

Is that the case? I was under the impression that Decimals were used in financial contexts because (besides preventing floating point error) you can define how to handle things such as rounding behavior.

For instance, at least in Python, 3//2 == 1 while -3//2 == -2; integer division is rounded down, and not towards zero as one may expect. Decimal lets you pick how you want that to go.