While tithing is part of the Old Covenant arrangement God had with Israel for the support of the priests, the New Covenant does away with tithing as required in the Old Covenant. There is no longer a Levitical system of priests to support. We have Jesus as our High Priest and as believers we are now considered a part of the priesthood. Consider the following verses:
Ye also, as lively stones, are built up a spiritual house, an holy priesthood, to offer up spiritual sacrifices, acceptable to God by Jesus Christ.
1 Peter 2:5
Note however, that while tithing is no longer required, giving is still a principle of God. As believers all that we have is God’s. We really should be praying along the lines of how much should I be keeping for myself, not how much do I give to God. And we believe God still honors giving, even structured giving such as tithing. Look at God’s promise to those who give tithes.
Bring ye all the tithes into the storehouse, that there may be meat in mine house, and prove me now herewith, saith the LORD of hosts, if I will not open you the windows of heaven, and pour you out a blessing, that there shall not be room enough to receive it.
Will He not also honor those who give from their heart? The apostle Paul tells us that God loves a cheerful giver.
Even so the Lord has commanded that those who preach the gospel should live from the gospel.
1 Corinthians 9:14
Therefore I thought it necessary to exhort the brethren to go to you ahead of time, and prepare your generous gift beforehand, which you had previously promised, that it may be ready as a matter of generosity and not as a grudging obligation. But this I say: He who sows sparingly will also reap sparingly, and he who sows bountifully will also reap bountifully. So let each one give as he purposes in his heart, not grudgingly or of necessity; for God loves a cheerful giver.
2 Corinthians 9:5-7
The ultimate answer to the question of tithing is found in your prayer closet. Seek what God would have you to keep, and then as a faithful steward of that which He entrusts to you, seek to know how to use the rest for His kingdom.
Give, and it shall be given unto you; good measure, pressed down, and shaken together, and running over, shall men give into your bosom. For with the same measure that ye mete withal it shall be measured to you again.
But whoever has this world’s goods, and sees his brother in need, and shuts up his heart from him, how does the love of God abide in him?
1 John 3:17