If you scan the item as you add them to the cart I don’t think it could be adjusted at checkout. For an old fashioned scan-at-checkout it obviously can’t know

If you scan the item as you add them to the cart I don’t think it could be adjusted at checkout. For an old fashioned scan-at-checkout it obviously can’t know what the price was when you added it to your cart, so presumably you risk finding it has a different price at the checkout than you saw at the shelf. Only way to avoid that (and probably the most common practice) is to change prices e.g only nightly.