Charitable Deductions

I serve on the boards of two different charities, I often donate items the office needs, or general supplies.  When listing  under the "item" category, none of the choices seem useful.  For example, if I purchase paper towels for the kitchen, or soap for the restrooms, or paper or ink for the office I buy them at the store and save the receipts.  Do I lump my receipts under "money" or do I list each thing individually?  Please advise.