Billing out for expendables?

[w802h]

I do my projects T&M.  Most of my consumables get billed at the point of purchase with any extra carried to another job.  If I use 2/3 of a bottle of glue I'll replace it on a slip to the job that the client gets a copy of.  There's always something that I don't have to buy and something extra.  It's usually a net benefit to the client.  I'm afraid of how billing 20 cents for sandpaper would look on a bill, so a lot of these items are built into my wage.  Trust and transparency in billing mean more to me and my reputation than quickly recouping these costs - not that it's in any way dishonest.  I try to think about what the client thinks or how they will react when they review a bill.  At the same time I think it's important to be cognizant of costs.  I just threw out 3 5 gallon pails of paint chips from my cyclone.  Brand new buckets and lids are actually cheaper than vac bags, especially if they previously contained pickles from the local deli!