sale prices incorrect at registers

I keep getting charged regular price for sale items. Since i get email receipts i don’t notice till i’m home, and it seems petty to go back for a dollar or so. Also since i receive the low-income discount i don’t want to complain. But many times they are things i’m only buying because of the sale price, or i buy several to stock up – to later see I was charged the full amount is frustrating. It happens at both stores. It seems like the price isn’t entered into the computer system. I try to pay attention as the items are getting scanned, but it’s hard to do while also (inevitably) chatting and bagging groceries. It’s starting to add up though over the last several months that i have been noticing this.
Thank you! I <3 OFC!