That's specifically a USA problem only. In the rest of the world, the price you see is the price you pay (not inc. restaurant service fees, etc, which are more BS exported from the US)
There is zero reason that the price sticker on a shelf or menu shouldn't be what you actually pay. It's not like online shopping where they need to calculate shipping based on distance, or tax based on state of the receiver. And there is no reason they couldn't even put both prices on the sticker.
But in America, they do it for one reason: capitalism. It's a marketing scheme. Makes you think you're getting a better deal and paying less while you shop, so shoppers tend to spend more.
It's why fuel costs $2.19 ^99/100
Because that's seen as cheaper than $2.20.
Sorry, but they're not going to be rounding that final price down to save you 1¢.
In short: you're as much a victim as everyone else.
Taxes don't vary inside a store, you idiot. There are no physical stores that straddle state lines and charge you different amounts depending on which checkout you use.
I'm going to guess you're both an idiot and you didn't read my second paragraph where I mentioned this specifically.