Get yourself an inexpensive (but cute enough to keep out on your dresser) piggy bank for your change. Whenever I buy something with cash, as soon as I get home I toss the change in the piggy bank. Make it a habit to toss your change into the bank every day! It's amazing how quickly it adds up!
This money is NEVER spent for household stuff, mind you, it's for hobbies and for when the 'Grands' come to visit. I always have enough to take the 'Grands' to the movies, the book store, etc. and it doesn't break the bank.
My piggy bank also came in handy right after hurricane Sandy. No electricity meant no access to ATM or credit cards. We had $45+ in the money jar...and it came in very handy!