I buy too much to add as I go along but I buy mostly the same stuff every week so I have a rough idea of how much it should be, what I always do is put all the BOGOF stuff and other offers together at the front of the trolly so I can immediately check that I have got the savings, I've had to go to the Customer Service on a disgraceful amount of times because discounts haven't been honoured. Don't get me started on shelf stacking and pricing, they seem to put up a special offer, then fill the shelf with a similar non offer product.