Ehhh I wouldn't recommend it. It's hard to read the other person when you aren't on equal footing. Also if she shoots you down, you can never shop there again, and she is definitely telling the other workers about you.
I work in retail, and the cute cashiers get hit on by dudes ALL the time. You might think you got something between you, but odds are she talks to all the guys like that. Some people are just like that. "But she remember's my order!" She probably remembers 50 dudes orders.
There was this one girl who had a number of customers she hated, customers who would try to chat her up when she was ringing them through. She would be all smiles and engage in the conversation, but if she saw them coming into the store and had the chance she'd make me take the till and go hide in the back.
Opposite situation, but a guy I work with always used to chat with this cute customer, he thought the chemistry was there, he handed her his number on a piece of paper one day, and she never came to the store again. It's a lot harder to read people than you might think.
All that being said, if you're really attractive, then there is a good chance it could work out.