I guess you and I will disagree. I definitely include my tithing and church contributions as a tax deduction. And I think 99%+ of other members do the same thing. But if that's how you feel - that's completely up to you. The Church's position is that it qualifies as a tax deduction given all the effort the Church goes through to provide documentation proving that it is a tax deduction. But that's my opinion.

The Church of Jesus Christ of Latter-day Saints is a non profit organization. So all contributions are tax deductible, meaning that under the law that sacrifice reduces your taxable income.  
 
By not claiming the tax deduction all you are doing is artificially inflating your legal income. Properly reporting to the IRS your charitable contributions is not a sin nor a crime. The real crime is to be over paying on your takes because you are falsely reporting additional income that you do not have.