Are cashiers required to stand, as opposed to sitting, while ringing customers up?

Standing for eight hours or however long they work can be extremely hard on your feet.

I went to Paris France a couple of years ago, and at a grocery store there, all the cashiers were sitting on chairs while they rang you up. I don’t know if that’s true throughout Paris, I just went to the one store.

So I thought why don’t they do that here?