Matthew 23:23 "Woe to you, teachers of the law and Pharisees, you hypocrites! You give a tenth of your spices--mint, dill and cummin. But you have neglected the more important matters of the law--justice, mercy and faithfulness. You should have practiced the latter, without neglecting the former.Some of us would give $7.50 more on our own but because of taxation we dont have that option. Charity cannot be forced or it is no longer charity now is it? Also you should study a bit on old testament titheing and you will find that the 10% tithe was a Jewish tax that amounted to income tax. The Jews were then able to give over and above that as charity. We (Christians) dont pay Jewish income tax and it never had anything to do with Christianity except when misunderstood and misapplied by folks -- often folks who were the recipient of said tax/tithe or folks that thought they were better than everyone else for paying it.
EDIT: Did a little bit more reading on the old testament tithe and it was actually unlawful for anyone who was not of the tribe of Levi to accept a tithe. Jesus could not lawfully accept a tithe (and He did not accept one). So unless your pastor is of the tribe of Levi and can trace his lineage to Aaron then it is unlawful (under Jewish law) to accept a tithe. Interesting, eh?
This is also found in red in the Bible meaning Jesus personally said it.
This argument is way off topic, but I am ok with that if you are. Christ said he came to fulfill the law, not do away with it.
(Matthew 5:17"Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfill them. 18I tell you the truth, until heaven and earth disappear, not the smallest letter, not the least stroke of a pen, will by any means disappear from the Law until everything is accomplished. 19Anyone who breaks one of the least of these commandments and teaches others to do the same will be called least in the kingdom of heaven, but whoever practices and teaches these commands will be called great in the kingdom of heaven. 20For I tell you that unless your righteousness surpasses that of the Pharisees and the teachers of the law, you will certainly not enter the kingdom of heaven.
He also explains that under that law we are commanded not to kill, commit adultery, etc. But that now, under grace, (eg new testament) if we have have hate in our hearts toward our brother than we have committed murder in our hearts and will be subject to the same punishment. Or if we lust after a woman in our heart than we have committed adultery (see Matthew 5:17-47)
So if under grace we are held to a higher standard than the Jews were held to under the Law, than how can you say the tithe is Old Testament alone? It appears clear to me that if you are a Christian than you are called to be even more generous than a 10% tithe.
I would be glad to give you more proof that your claim of a tithe being an Old Testament tax on Jews is inaccurate (although highly accepted in our culture) if you would like. It is a topic I have spent A LOT of time researching. (There is more scripture about money than just about any subject in the Bible. I think God knew how to get our attention. )