Absolutely. If they're not going to take the cost of the labor off my bill then I'm just doing them a favor by letting them hire one less cashier while shifting

Absolutely. If they're not going to take the cost of the labor off my bill then I'm just doing them a favor by letting them hire one less cashier while shifting an unwanted burden onto myself. The worker scanning and bagging my groceries is a service that makes my shopping experience more pleasant and less taxing on me. I'm not giving that up in exchange for nothing.