"Pretty pence" is often used to describe a small sum of money, but there are plenty of other synonyms to choose from that can add a touch of variety to your vocabulary. "A few coins" or "a handful of change" both suggest a small quantity of money. "A meager sum" or "a paltry amount" convey the idea of limited funds, while "a drop in the bucket" implies that the amount is inconsequential. "A token gesture" or "a mere trifle" could be used to describe a small payment that is not meant to be taken seriously. Whatever your context, there are plenty of ways to describe a modest sum of money without relying on the term "pretty pence".