Almost every store these days puts your items in plastic bags. But, these bags not only work as temporary carries for your groceries or household supplies, they work great as trash bags for your trash bins.
Most stories give you a different sized bag based on the size and number of items you are purchasing. The bigger bags can be used for bigger trash bins, and the smaller ones -- you guessed it -- are perfect for small trash bins.
So now when you are running low on real trash bags, you have a great backup option!