To make things easier for tax purposes it is easier and less confusing if you use a credit card. Even if you have no credit you can still buy a pre-paid credit card. With either a pre-paid credit card or a regular credit card you have a receipt you can save for tax purposes. Also if you lose your receipts yo can always ask the credit card company to give you coppies of your statements and receipts...
I always keep all kinds of receipts specially the tax ones. You can claim or even refund from your income tax by showing these receipts and its always good to have a copy of it.