There are some receipts that it is very important to keep (and I'm not talking about the receipt that you get for dropping $50 at the pump last week).
One example is a receipt that you may get from selling a car. If you sell a car you should get a receipt, you have to get the title changed (which entails going to the MVC (formerly the DMV) and doing some paperwork), and you have to bring in the old license plates. If you don't do these things you may end up getting tickets for bad things a future owner of the car does.
I recently was in court when a prosecutor asked for a sales receipt of a car from several years ago. Keep those receipts.
Another example is a receipt from paying a restoration fee to the MVC. If you ever get suspended in New Jersey you have to pay a restoration fee, usually of $100. MVC used to give you a pink receipt - and they still do if you pay in person. Keep that receipt. You can print out a receipt if you pay online, as well.
If you pay a fine for a ticket you should keep that receipt. Mistakes have happened (passive voice) and you want to be able to prove that you were responsible.
I know keeping receipts is a hassle but you never want to be in a position where you wish you had one.