My wife and I switched to using all cash for two months for purchasing items. (groceries included) Though we pay our credit card balances in full each month we wanted to see the money leaving our hands for each purchase; there should be no difference right? :)
All we did was make the decision to get money from the ATM each week for what we thought was reasonable for each of us to spend on groceries, gas, dining out, and all extras. We budgeted the same amount of cash each week and we used our credit card purchase history to help determine that weekly amount. Thursday was the wallet refill day and come the following Tuesday/Wednesday things got tight early on.
What we learned:
1) We got mad the first two weeks because we both ran out of cash way soon.
2) We could do better with the 'extras' category of spending, like cut most of it out.
3) We found ourselves putting money aside each week to buy something bigger in a future week.
4) Those items we were 'saving' up for ended up not seeming important after we had cash money to buy them. Guess we did not need them.
Overall we are glad we did this, it was terribly inconvenient for buying gasoline, but we saved money without really trying to. We are both back to using our credit cards (we continue to pay the balance in full) but we are both glad we went 'old school' with cash purchasing. It opened our eyes to what we needed vs. what we just wanted right then.