This is my personal opinion-
Yes, I would. When they scan something, if it comes out less than marked they will usually give it to you anyways and it makes you look good. (Normally the item is on sale but the tag fell off so the price is correct.)
I have also gone back to the store when I noticed that they didn’t charge me for an item. Again, I didn’t have to but it made me feel good.
A friend once wasn’t charged at Staples for an expensive toner and asked his R”Y what to do. He was told that he was allowed to keep it but he won’t see any mazal with anything it’s used for. He called the corporate HQ and they told him to enjoy it.