She seems to be around my age.
Why do women have to be around your age? This is nice guy pleaser bullshit mentality.
There are millions of young women who are looking for fit, older men because, honestly, most guys takes decades to not act like children.
Age does not matter for men in pickup, fitness does.
As far as gaming the clerk, I don't have a whole lot of successful experiences with that. Perhaps something like having her give you a pen. Then write your name and number on your receipt and give it to her. Tell her that she seems cool and to call or text you after she gets of work. You're not asking her a question, it's not needy or creepy, YOU are TELLING her she is good enough to chill with YOU, and it puts the ball in her court to actually contact you first to show her interest.
Just whatever you do, don't ask her anything in question form. You simply state how everything is and what you are going to do and show your intent and maintain a solid confident frame.