I thought I should maybe make mention of food safety with the reusable grocery bags. Make sure the ones used for food are only used for food if at all possible. There is a distinct possibility you could get ill because hamburger leaked on to the bag. Yes, you do need to inspect them periodically and clean them when you see food leakage. I would also recommend grabbing a store bag for meat separately. Of course, if the city has made it illegal, like Chicago that won't be possible and you'll need to bring your own but make sure they are clean.
Go ahead and use them but be careful. They do save the environment in so many ways. Now for boxed and canned goods there probably won't be any issues and I've never had any in the last six or seven years.
Each of those bags does cost about 2 cents each. That gets into what the store charges you for the items you buy. They are not without a cost to you. So, if you want lower prices at the store bring your own bags and make it a habit.