I'm fairly used to this and will always offer to show the cashier my purse full of student cards etc which have the same name and date of birth and a better (often inappropriate for a driving licence) photo but which are not valid ID. If they say no, fair enough, they're doing their job and I will thank them and try elsewhere.
Yesterday, however, the cashier responded to this request by adopting a babyish voice and pouting expression and going "Look, I'm sorry your little fake ID didn't work out but I'm not selling you cigarettes. Try harder, yeah?' then showed my ID to her colleague while laughing about my attempt. Her colleague looked decidedly uncomfortable and I'm fairly sure my eyebrows had risen high enough to disappear from my forehead when I asked for my ID back and left