Tarlton,
My wife was the financial officer for our company, so she knows a few things about tracking expenses.

She is both good at that sort of thing and I think she actually enjoys it as a hobby.
She extracts every single printed receipt and credit card charge, no matter how small, and enters them into her tracking system. If I make such small individual purchases as a roll of duct tape or a bottle of baby powder for the diapers, or sea salt or Castile soap for my enemas, it all gets tracked - and adds up!
It is easy for us to remember to keep track of major expenses like cases of disposable diapers, a new batch of cloth diapers, or catheters; it is the small things we either forget or fail to keep a record of for the IRS if audited.

That is the catch - if audited I have the receipts to prove the expenses. Admittedly, if left to my own resources I would not have been so thorough.
--John