One thing is certain - we cannot tithe in accordance with the Torah commands as there is no Temple or priesthood to support. If I understand it correctly the tithe to the Levite's was their inheritance and it was given in animal and agricultural products by the owners of the land of their increase.
As far as I know the working man did not tithe - since he was trading labor for income he had no increase even if he was paid in kind.
Lev 27:30 And all the tithe of the land, whether of the seed of the land, or of the fruit of the tree, is the LORD'S: it is holy unto the LORD.
Lev 27:31 And if a man will at all redeem ought of his tithes, he shall add thereto the fifth part thereof.
Lev 27:32 And concerning the tithe of the herd, or of the flock, even of whatsoever passeth under the rod, the tenth shall be holy unto the LORD.