Talking to a cashier is reallly easy. I ring people up all day, i always small talk with them, ESPECIALLY the female customers.
Heres an example. Today one of my coworkers was helping this really fine blonde HB 8. Well i was at the register next to my coworker and i overheard the HB say "5 years". I made a decision to interrupt the convo and see what the fucc she was talking about.
I said "What did you for 5 years?
She then said "Oh, i went out with this guy for 5 years, from age 13 to 18 (she was 18 btw). I replied back by saying "Damn that is a long time, and pretty much a waste too huh" And she totally agreed, she spoke enthusiastically and we had good eye contact.
We then just went back and form for like a minute about the worthlessness of long term relationships during your teenage years etc and that at this age we should be having fun and sh1t like that.
I also noticed she was very polite and receptive, for instance, she was saying something and i interrupted her and added in something which stopped her for a second, then she was about to say something else but i kept going to add in another statement and she stopped like instantly and we held eye contact and she seemed very interested in the convo.
She was so hot and she visits the store often, i wish we could ask customers for numbers but we gotta keep it professional, ya know. So now im just waiting for her to ask for my number.
Btw dude, just because shes at work doesnt mean she cant accept numbers. She may like you but cant do anything about it or she may be fired. Its in your best interest to initiate conversation. You must ask for the number.