Don't spend a dollar on a special rubber band for every trashcan you want to fix! Spend 1 and 1/2 minutes plus $0.04 of material! This comes out to $42.60/hr in savings. Do you get paid over $40/hr? Do you want to :D? Yeah... so here's the trick:
Step 1: Build the Band
Materials and Equipment Required:
1) Yarn(at least 4 feet)
2) Rubber band(thicker is better)
1) Wrap a length of yarn around the top of the trash can.
2) Cut the yarn where it meets itself.
3) Tie a rubber band to one end of the yarn. See Pic #1.
4) Tie the other side of the rubber band to the other side of the yarn and leave a 3" or 4" tail. See Pic #2. This should have taken you around 1.5 minutes.
5) Slide over trash can to hold the edges of the bag down. This will be plenty of force to keep the bag held fast. I've been using this successfully for a few years. In fact you can modify this trick any time you want a long stretchy thing. See Pic #4.
6) Marvel at both how little time you have spent and how much time and frustration you have avoided!
This took me about a minute and a half from "hey I want this" to "Yay! I have this".
I also inserted a video on how to make this.
Like Mr. Franklin said: "A penny saved is a penny earned."