DD1 didn't enter a supermarket from the age of 11m until about 2y due to tantrums. I used to do the shopping at night when she had gone to bed (bliss).

Now she is an absolute joy to take shopping - we go tot he Coles that has the kiddy trolleys and she pushes one around with me and fills her trolley up with the stuff she can reach and she unpacks it on the conveyer. She is a great help and she even entertains DD2 while she is stuck in the trolley. So in my experience it does get better but you may have to wait a little while...