I bet they can add up to a pretty penny if you aren't careful.

我确信如果你平常不是很小心的话，这些账单的数目还是相当可观的。

youdao

The conference also urged the executive to support the Liberal Democrat policy to add a penny onto the basic rate of income tax, provide teaching facilities in Gaelic and other minority languages where there is demand, and ensure that class sizes are reduced across the whole age range of pupils.

BBC: Conference hears exams call