a little help?

Shawn and I just sat down to go over our budget. We use the mvelopes system online and both really like it, BUT I seem to have a problem that I need a little help with. See, in order to utilize the mvelopes system to its fullest you really need to keep and enter ALL receipts. I will be honest with you guys - I have the hardest time holding on to my receipts. Sometimes they get smashed into my purse, sometimes they go in my wallet, sometimes they stay in the bag with my purchases, and sometimes they go flying across the parking lot never to be seen again. What do you do to keep your receipts organized? I thought about getting a ziploc bag or just a mind that remembers but I thought I would ask you all first. Thanks in advance for your amazing answers and for saving my marriage!!!!