I just have file folders that I put receipts in every month. I get a new one each month, file the old one. It's worked quite well. Then, when tax season rolls around, I can quickly sort them into categories, and make spreadsheets to total things up.
And, don't forget, if you use your personal car for delivering things, going to the post office, buying office supplies, etc. you can count the mileage as a business expense.
