First you'll need your food items. Scrunched up tissue paper tied with a rubber band and tossed into a net bag will make instant oranges and apples.
Pantyhose stuffed with newspaper and voila...baguettes! Sadly, we're actually getting hungry...
Roll up some thing dish sponges and secure with a rubber band and you've got sushi rolls.
Now for the all important cash register because yes, after you help them create them, they'll be charging you for these "food" products. All you need to make this cash register are the basics: paper, pencils, cardboard boxes, paint, glue, tape, a foil tray, scissors, and some string.
Check out all the how-to's and some other great pretend food right here. They also have a good list of fun play food/shop items you can purchase if you are so inclined.