Teller is only at a bank. Full name: "bank teller". Cashier is very common. The person taking money at any business is a cashier. Anyone that stands at a cash register. But a teller *gives* money, so it's not a cashier...

depends on the situation- when paying for something at, say, a store, i would use the word cashier. but when i'm at the bank i would use teller. teller usually implies a banker while cashier implies people who work in a store.