Slow: do it by hand.
Stupid: use a Coinstar machine. These machines charge around 8 cents per dollar. That’s a whopping 8% tax just for the privilege of letting a machine do it for you.
Better: some bank branches have change counting machines that will count your money for free. Call around.
Best: just take your spare change with you next time you go to the store. Use the self-checkout isle, and cram coins into the machine until you paid your bill.
When I do self-checkout, I first empty out all my coins, then I use $1 bills, then $5 bills, etc. This way I am guaranteed that whatever change is returned is the lightest possible combination of currency.