Please note that for tax filing purposes you do not have to include receipts with your tax return filed with the IRS. However the IRS can request a copy of your receipts for review and you should always keep a record of your receipts for any purchases you might be eligible to claim on your US tax return.
Your records should include bills, receipts, invoices, cash-register tapes and any other original documents that provide information about the purchased item, such as purchase price and tax paid. These may be maintained in an electronic format. The provided receipts/bills etc. should also show the rate of tax collected on each sale and any use tax you paid, if any.