After battling it out at the petrol pumps, supermarkets could be gearing up for a new price war - this time on their groceries.
Sainsbury's is currently trialing its new Brand Match technology in 12 Northern Ireland stores. The technology calculates the cost of customers' shopping items at the till and checks to see if the trolley of goods would be cheaper at alternative supermarkets.
Brand Match compares prices on over 12,000 branded items to Tesco and Asda prices.
Mike Coupe, Sainsbury's group commercial director, says it "marks a huge step forward in the supermarket shopping experience".
"We want to give shoppers a no-hassle experience; we understand that they don't want to spend time constantly checking prices or logging onto a computer to print out a coupon at home. Quite simply, we're doing the maths and the work so they don't have to," Coupe adds.
Customers using Brand Match are instantly rewarded with money-off coupons at the till.
Both Tesco and Asda offer similar schemes, but shoppers have to check prices online and then redeem vouchers.
Tesco's Price Check promises to pay shoppers the difference in price if they find their Tesco-bought items are selling for cheaper at Asda.
Meanwhile, Asda's Price Guarantee Scheme promises shoppers its products will be 10% cheaper than the equivalents sold at Tesco, Sainsbury's, Morrisons and Waitrose. The supermarket promises to reimburse customers the difference plus an additional 1p.
How to beat the supermarkets
While supermarkets battle it out to claim they're the cheapest, shoppers can play the stores at their own game and get the price possible.
1. Compare prices
As well as using supermarkets' own price checkers, you can compare prices on mysupermarket.co.uk between Tesco, Asda, Sainsbury's and Ocado. The website allows you to save favourite items into shopping lists too so you don't have to do the virtual shop every time you log in too.
2. Buy local
Farmers markets and fancy delis won't cut your shopping bill but local greengrocers and supermarkets might. For example, instead of buying a small jar of spices at the supermarket get more than double the amount for the same price at an Indian supermarket. You can also buy fresh fruit and veg that isn't pre-washed, sliced and diced to cut out more costs.
3. Go budget
Stores like Lidl and Aldi are no longer the laughing stock of the shopping world. Smart shoppers know they can get good quality groceries and many are heavily discounted as part of Aldi's daily price cuts, while Lidl asks users to type in their postcode online to find out about special offers close to them.
Read Rebecca Rutt's blog: Why shopping at Lidl makes total sense
4. Get cashback
Mysupermarket is a cashback partner with both topcashback.co.uk and quidco.com, the country's two biggest cashback websites. They reward shoppers with £5.05 cashback on their shop. Individual supermarkets also run offers, but how much cashback you get and the products it applies to will vary.