I think tithing is only mentioned twice in the New Testament in regards to the old law. If you wana keep the law make sure you dont wear any mixed fibre clothing and guys need to keep their beards trimmed according to the law.
However, the new testament talks alot about giving ...and giving with a gladful heart....its all about if you see a need and you can do something to help then do it. Living by the spirit, being lead by Him to know what to give and where at the right time. Those that follow the law give their 10% to church and then switch off. When we give our lives to the Lord we give ALL our lives...including Him ruling over our finances.
i usually find that churches that still preach on tithing but disregard the rest of the law are usually those that are relying on the congregation for money and not trusting God.
This is exactly the right answer theologically, but I want to add to it practically.
I know a Jewish story: The rabbi takes all the synagogue collection money, puts it in a big tub. He tosses it up in the air, and figures God will keep whatever He wants. Then the rabbi can keep whatever does not stay up in the sky.
There is a point: God keeps nothing, because He has entrusted it all to you, to be used on this earth. We do not live here. We live in the Kingdom of God. What are we doing here? We work here, to build the Kingdom of God. The money is for that.
When you eat, you do it so you can be stronger to help build the Kingdom of God. When you sleep, same. When you buy clothes, it is so you can be presentable to build the Kingdom of God. Even when you go to a movie, or pay for cable TV, you are getting recreation, so your mind can be clear to hear the Holy Spirit. If you are living as you should, 100% of your activity is either building the Kingdom, or supporting yourself in the world so you can build the Kingdom. The real question is, what percentage is your church playing in suporting, or being part of that ministry?
In proper balance, pastors teach tithing as a lesson, for those who are not ready for the meat that TwoFeet and I posted. There's a time to learn, and a time to step into your own ministry. I suspect that's why you are asking the question.