She took my $22 and held the 2 singles separately as she rang in the 20 then told me I gave her too much.

If as you say she was only reacting exactly how she was trained, then we have another discussion. One around those who claim minimum wage should be sufficient to support a family. There’s a very good reason why it isn’t at that level. It’s intended for those incapable of thinking outside the limits of their training. Those who can, get promoted and earn more.