how to know if the cashier is flirting ??

Didn't you ask about this before? She asked about your coins or something that a real cashier might ask?

YOU need to be more direct if you want to check out a flirt.

Look her in the eye and say, "Hi."

There was this girl at a supermarket near me. She smiled at me and said "Do you want to pay by card or cash?" but I knew she wanted me so I waited for her after work. Next thing I knew two security guards had hold of me and she was yelling "That's him! He's that weird guy!" I guess she must have had a better offer. I bet it was that guy buying potatoes and beer. I'll never understand women.

Put it down to "that time of the month", and move on.

I would talk to him about something not related to work.

I would hope that if he was interested, he would talk to me.