I always check all items on my receipts and then the total again against my bank statement as I tend to pay for everything by credit card and then pay the amount in full every month. That means I can collect loyalty points for something I would spend money on anyway.
Tesco will always give refunds without question, I find, if a mistake on price is made. I just take the empty package back next time I shop there, especially if I only bought something which was reduced, only to see on the receipt that it had been charged at full price.
Last week, I bought a packet of mixed salad leaves reduced for 25p to sell that day and, at home, saw the reduced price sticker hadn't covered the original and I was charged £1. Tesco refunded me £1.50. So, I made a profit and had free goods too! It's always worth taking things back if you are charged incorrectly.