Now, an investigation by consumer organisation Which? has exposed range of supermarket pricing tricks designed to catch you out.
Deals are everywhere - for example, an average of a third of Tesco's 30,000 online products were on offer every day during July.
A popular tactic used by supermarkets for over a year now is the 'round pound' idea where prices are rounded to the nearest pound. While many of these offers do mean cheaper products, some prices have gone up as a result of the rounding. Out of 1,000 products rounded to £1 or £2 by up to 20p, Which? found 587 led to price rises.
Professor Paul Dobson, head of Norwich Business School, says: "This tactic signals simplicity and big value, but you'd rarely remember the price before it became a 'round pound'."
While loose fruit and vegetables are often priced per kilo, pre-packed versions come with a single price, making it difficult to compare prices.
Multi-buy offers such as yoghurts are there to boost sales volumes and it inevitably leads to overbuying, with some ending up in the bin.
However, you can still get some great deals if you focus on what you really need.
We have blogged about some other tricks of the trade of supermarkets. If you're serious about shopping around, Mysupermarket.com lets you input your shopping list and tells you how much your shopping will cost at different supermarkets, although it doesn't include the discounters, Aldi and Lidl.