If you shop at Aldi I would urge you to check your receipt. On two separate occasions in the last three days their scanner as scanned an item twice, their scanners seem to be far superior and very sensitive to achieve speed at the checkout. The first time it happened on Sunday I didn't check until I got outside, a box of almond tarts at £2.49 cost me £4.98.
I went back in, only to have to stand in a long queue, as they have no service desk, got my refund, with a few dark looks off customers and the till operator for the hold up I was creating, and informed by the till operator that it does sometimes happen if the scanner picks the bar code up at the begging of the swipe, then again half way through.
Yesterday it happened again different store, but I picked it up as it happened, the till operator didn't ( LOOK OUT) Zap down your receipt you will soon see the double item together.