Keep grocery spending in check without losing credit card benefits

I use my credit card to buy all my groceries because I get 5% cash back on each purchase. That adds up to a decent sum over a year, so when I was looking for ways to keep my grocery spending in check I didn't really want to switch to the cash-in-an-envelope method (put your budget amount in cash in an envelope, pay from that, and when it's gone it's gone). I think I found a compromise, though, that gives you the best of both worlds.

If I buy a gift card at the grocery store, it should register as a qualifying purchase on my card and hence get the 5% cash back. But it will also have a fixed spending limit that I can then use for the rest of the month, and when it's done it's done. The credit card company got the money (and associated fees from the merchant) so they're happy. I get my built in budget tracker, so I'm happy. Win-win!

I have to check with the credit card company this week to make sure that all purchases at a grocery store qualify for the cash back to make this work, but if they do I can't wait to put it into practice. If you try it let me know what you think!