I sometimes use a cart but not that often. I am really impressed with how much "stuff" I can get on that little scooter. I can usually put 2 to 3 plastic bags in the top box, 1 or two bags of dry goods and cleaning supplies in the pet carrier, a case of juice or pop and a pizza strapped to the seat with a cargo net and a bunch of cold stuff in my new cooler bag. I take the cooler bag into the store with me and pack it at the check out.
I also have a special bag that I hook to my carabiner hook under the front of the seat where I usually put fresh baked goods. That pesky french bread doesn't fit in any of my carriers!
Oh, and if I have to buy toilet paper or paper towels or anything light yet bulky, I have flannel bags I made out of old bed sheets that I tie onto the seat rail and they ride side saddle. The flannel is kind to the paint and polishes the cowls while I ride!