The sooner you disabuse yourself of the notion that you are a "person" with "rights" and "feelings," the easier it will be to handle the fact that you are simply a "resource" your employers grudgingly have to pay to facilitate the extraction of their constitutionally protected profits from "consumers."

What part of town do you work in? As a customer, I enjoy exchanging a few pleasantires with cashiers. I have picked up some very good recipes from cashiers at Freddies. Sorry that people
are jerky to you. Try to let it go- they have to live with themselves. That's how they treat their spouse, their co-workers. Be the better person and people will feel more comfortable chatting with you. The customers who appreciate cashiers are out there.