I take and store every receipt I am offered, even optional ones (which isn’t very “green” of me, I know… sorry) because I check all the charges on my credit card every month. However, aside from saving paper, there is a new, very compelling reason to avoid cash register receipts whenever possible. They contain BPA, which is a dangerous toxin we should all try to avoid, and it has been shown that BPA rubs off on your hands very easily. Here is a recent article and another that discuss the issues. If you’re not going to read the articles, at least do this, as the second article recommends:
At least pregnant women would know to wash their hands after picking up a BPA-laced receipt. And we’d all know to keep such paper out of hands of kids. We might also want to store those receipts in some zip-it-closed plastic baggie, not our wallets.