This sort of thing is becoming rampant at least in my locale, so watch for it.
Not very long ago, a chain called Dollar General (think "Poundland" for those of you in the UK reading this) was heavily nailed by the PA Attorney General's Office because they labelled prices on items at one price, but the receipt would show a different one, invariably higher. If you protested, the clerk would say that was what was in their "system" and he or she couldn't do anything about it.
The AG nailed them for fraud over this, the law says the price would be that advertised and labelled, not "the system".
I've been more aware of this sort of thing, so spot-checking things like the supermarkets and anywhere you buy multiple items and just take the totals of many items by faith. So far, I've found several grocery chains doing this, all of whom refunded any disparity without question, but how many times do they get away with it compared to the one pedant that checks?
The local un-named fast-food place is doing it, too. Here's their board and here's the receipt. This time, they declined to make it right after going through the "its the system" bullshytte. Its a dime, but its but one item in a day's receipts and its thievery.
It ain't enough the current administration says one thing about their anti-inflation priorities yet demonstrates a dismissiveness and apathy that puts paid to their rhetoric (Quelle surprise!), but the retail industry in America is resorting to this sort of systematic fraud on top of their already rather famous "shrinkflation" misrepresentation in packaging.
Spot check any of them, call them out, photograph the evidence and turn them in. They are stealing from you while you are struggling to make ends meet.