Any tips for a AFC on improving my game while at work? I'm a cashier at Target so I'm constantly talking to people. How can I use my job to improve my PUA game?

Well thats kinda a good start.

What you could do is game every one be that cheeky friendly guy that chats to everyone and flirts with old ladies (within reason dont want you to lose your job) what youre doing is building a lifestyle, You want to do is be the cashier that all the customers go to coz youre the friendliest and funniest that way youre building social proof which will help you with youre game.

Dunno if thats any help dude?

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60% of the time it works all the time!

Start by "hitting" on ugly and old chics and work your way up. Keep it low key though cause you are supposed to be semi professional. One of the best ways to flirt is by not making the person think you are flirting, which is perfect in your case.
Tease, tease, tease if shes buying a crappy movie scan it and while bagging dis on her taste. Sober faced and looking at the next item to be scanned say, "Ohh, shoulda gone with your first choiceon that one, but too late now the transaction has been processed." Be prepared to recommend a better movie, or if she has an excuse say "there's no need to explain to me I am just your cashier."
Watch yourself though...

While I was at work today a HB6.5 was totally eye fucking me and smiling/laughing while I was making silly jokes. Is there any way I could ask somelike this out while workin or should I just let her go? I ended up saying I'll see you later and she smiled back and said bye.

IMO, you should just let her go.

If you do want to try closing, though, seems like the only thing you really can do is just SOI and ask for her number. No guarantees that you'll get anywhere, but worth a try. You'll need ridiculously strong phone game, because you won't get the chance to learn much about her, tell her about yourself, or kino.