I'd bet there're a number of retailers who 'claim' they're collecting tax to send to your state, but don't. Nice way to pad a little 8-9% profit margin. Of course, if they get caught, they're in trouble, but who's really policing that? Someone from OK auditing sales records from a company in AZ or FL? I don't think so...
I don't know how all states do it, but they bill that crap by the county, and quite possibly city, in Kansas. Since anyone that does collect, collects my county's rate. I live in one of those towns of less than 100, so there ain't no city. SG is the last holdout that doesn't charge tax yet, and that's one of the reasons they're getting pretty much all my ammo business at the moment.
I wouldn't want to get caught on a deal like that. My business has to collect in Kansas, and it's absolutely asinine since I'm a service business. I keep my nose as absolutely clean as possible since I operate heavily in two states. There was a guy early in my career that got busted not charging it, and it wasn't a pleasant experience for him.