How far do you go out of your way to correct a cashier error? Do you go back in only if you're still at the store or go back the next time you're there? What if it's not a store you go to a lot? Does it make a difference if it's a big error (let's say $20+) and/or if it's a small chain vs a big store.
I was at Lowe's yesterday. I'm normally very honest but this one was just ridiculous negligence. I bought 2 of 2 different items, then 4 single items and 4 of one item so 11 total items. I was charged for 3 single items. Total was $23 and change. I had already swiped my card while she was ringing and bagging and had DS with me so I didn't even see the total till I got home. I honestly don't know how she wouldn't get in trouble and then I'd feel bad but now I feel guilty not getting it fixed either. I have no idea how much some of what I got was but I'd guess the total should have been $50-$60.
I wouldn't go back, but I've noticed with HD/Lowes sometimes they're not good about counting things that are similar.
I had a horrific HD checkout experience and I think I had to tell the cashier how many of every item I bought more than 1 of b/c she wasn't paying attention.
Since you were already home and had all of your stuff out of the bags, I probably wouldn't go back. I generally watch what the cashier is ringing up and check my receipt when I get to the car. I've found that going back to a store to fix this sort of thing, especially a big box store that hires anyone and everyone, usually results in mass confusion and will take a load of time to correct. If it was a small store, since they generally have less hoops to jump through, I'd be more likely to go back and let them know.