Probably no one will be able to claim the deduction.  You can’t claim the deduction for a gift of cash without an acknowledgement from the charity, which you are not likely to receive, or a bank record, which you won’t get from the store.  That’s one of the new rules from the Pension Protection Act of 2006.  (See Ready Reference Page: “Congress Passes Charitable Reforms.”)  The store can’t claim a deduction because your gift is earmarked for the charity, and is not a gift to the store.

If you are going to make contributions like this, you may want to do it where the gift is added to the cash register tape and identified as a contribution.  It is less likely to be diverted by someone with sticky fingers. Or, if you put it on your charge card, with your store receipt and bank record of the payment, you will probably have sufficient records to claim the deduction --if you think it is worth it.