It is a mandatory tithing, more of a tax.
When the cult leaders can demand your tax returns to verify that you are coughing up a verified amount, and when you cannot get past the Temple door unless you comply with the mandatory 10% fee, then calling it a tax is not a stretch.
Pillars of Mormonism, pillars of Islam...all vain attempts by man to reach up to God.
The Good News of Jesus Christ is that God reached down to us.