Matt Barry wrote:
I used to work at a gas
station (for all of three days) and quit because of people who drove off
without paying for gas, and the clerk on duty had to make up the difference.

I'm pretty sure this is illegal for the employer to do.

I read an "action line" column in a newspaper where a reader wrote that
his employer would make the employees pay out of their own pocket if
they accepted any counterfeit bills. The columnist wrote that this was
illegal, and he should bring this up with the employer. If that didn't
resolve it, then he should take legal action against the employer.

This seems like a similar principal. The employer can fire you for it,
but they can't legally make you pay out of your pocket.