so that is a bad example (I'm a CPA and I know).
Notwithstanding, there is a BIIIG difference between tithing and a donation outside of it. Tithing is a commandment. Donations outside of that are not (although it could be argued that many have promised to consecrate all they have for building God's kingdom, but that is a different discussion).
Many people donate outside of Tithing, and I don't consider it sacred, like I consider tithing. If I donate a horse ranch to BYU (true story) to be used by their athletic department, are those funds "sacred?" I would argue that they are no more sacred than if I donated it to the Red Cross. However, if I took the same horse ranch and donated it to the Church as tithing, I feel that the money is sacred and should be treated as such.
The taxability of a donation has no bearing on the sacredness of the funds in my mind.