Is it permissible to take the extra change from customers while handing over the agreed-upon amount to the café owner and my monthly salary?

If the cafe offers prohibited items such as shisha, tobacco, and alcoholic beverages, then it is not permissible to work there, due to Allah's saying: "And do not cooperate in sin and aggression." As for the change left by customers, there is no harm in possessing it, because it appears that its owners left it due to their disinterest in it.