I've always felt guilty that I don't give ten percent of my income at church. (We've never called it a "tithe" in my church culture, as tithing was part of the "Old Law", and in the new covenant we just freely give, "although, ahem, ten percent is a good number to shoot for".)
But in the past couple of years or so I've realized a few things:
1) the Mosaic tithe was both a religious contribution and a federal government "tax" (since in ancient Israel church and state were the same thing). Today, our federal government already takes out 28% (or more) of our income, almost three times that of the Mosaic tithe. And then there's all the other taxes and fees in our modern world. I'm not sure that the Mosaic tithe is appropriate in our modern economy.
2) giving consistently is important. It's better to give $5 a week consistently than it is to plan on giving $100 a week and only meet that commitment seven times a year. (Yes, the church gets more with the occasional $100, but it does more good to the giver to be consistent.) God has strong words to say about not keeping a commitment, like Eccl. 5:4 - " When you make a vow to God, do not delay in fulfilling it. He has no pleasure in fools; fulfill your vow." Better to give less than a tithe and be honest in your giving than to vow more than you'll fulfill.
3) Although funding for preachers and missionaries and staff, etc, is Biblical (1 Tim 5:17-18, Luke 10:7), most of the emphasis on giving in the New Testament is for the feeding and care of the poor, elderly, orphans, displaced, etc. Currently most church budgets are more about paying off the building debt and paying the ministers' salaries. (This is not a blanket condemnation of all churches, especially since these are needful things.)
4) Being in debt is, more or less, anti-Biblical ("owe no man anything, but to love one another" - Rom. 13:8, etc), and I've been in debt for all my adult life. In the past couple of years I've been working to rectify that. But in the meanwhile, it seems that the New Testament indicates that taking care of your family's needs comes first when it comes to finances, then comes taking care of your debts (your vows), then taking care of others. In other words, you should not give money to the church if that means your kids go hungry or your grandmum doesn't get her prescription filled or you default on a bank loan, cheating the bank of their money. (But you also should avoid that bank loan to begin with (or credit card, more likely); I now see that living beyond your means is a sin (in most cases in America, (because of big-screen TV purchases, etc), but not all, and especially not for many in third-world countries, where you do what's needed to survive) -- we've failed, both as a church and as a nation, to teach these principles to our kids (or more accurately, our parents failed to teach them to us, and we learned the lesson (or not, in many cases) the hard way).
5) That oft-quoted passage in Malachi 9, which I've heard all my life, to test God by bringing in the tithe and see if he doesn't in return "pour out so much blessing that you will not have room enough for it", is a promise to the nation; it's not a promise to individuals, which is the way it's usually presented from the pulpit. I believe that what God is saying through Malachi is that if a nation does right by providing the tithe to God, "A rising tide raises all boats", and everybody benefits from the healthy economy. He is not saying that if Joe Schmoe tithes, he'll have plenty of money for his family's expenses. (So next time Brother Delbert on TV-For-The-Lord says that God has promised to bless you if you'll just send $50 to his ministry, be skeptical.)
So I don't give 10%, and I'm not feeling guilty about it. But I am, for the first time in my life, giving consistently, even if it's a very piddly amount.