Should a carwash owner take his employees tips?

My husband works in a carwash and the owner is always keeping an eye on the tips the employees receive. They get payed $8 an hour and if he sees a customer giving any type of tip; he will take it away from my husband and the others after the customer leaves. This absolutely pisses me off. Does he have the right to do this? My husband sometimes does a full car all by himself and a customer directly gives him a $10 tip for his work and his boss immediately takes it. He says he gives them a small percentage of the tips afterwards in their weekly check.