Definitely keep your receipts - they are your 'back up' documents should the IRS inquire - otherwise they have no way of knowing how accurate/truthful your spreadsheet #s are.
ALSO NOTE: MOST receipts are printed on a glossy type of paper that fades in as little as a few months - you really should consider photo copying them. I attach my original receipts to the photo copy and can get several receipts on one page.