(2 Corinthians 9:7) Every man according as he purposeth in his heart, so let him give; not grudgingly, or of necessity: for God loveth a cheerful giver.
this would have been a great place to talk about percentages, or who to give to...
if it bothers you to 'tithe', then you you won't be cheerful about it, and since God loves a cheerful giver, it could be assumed that He isn't pleased with a giver who is bothered by giving
if you 'tithe' so that you will be blessed, or so you won't be cursed, then you are giving of necessity - like paying off the mafia
give your gifts to God, and then let Him lead you on what He wants you to do with His money.