I have a relative that swears by the online grocery shopping. She says it's saved her a lot of money because she can stick to her list and not get tempted by bargains and special offers.
I can see the attraction but I like to choose my own foods and not let someone else decide for me, especially not the 16 yr old pimply guy that has other things on his mind than the quality of the sprouts he's choosing for me 
I agree. You benefit from the special offers by substituting them for another item from the shopping basket. This is possibly not from the current basket but from a future one, so don't forget to check the use-by date.
Incidently, there's something not-quite-right about your avatar but I can't put my finger on it...