I recently heard of an evangelist teaching that beyond the tithe, saints are required to give an offering of 5% of their increase. His scriptures for this come from
Exodus 30:13-15. What say ye?
Exd 30:13 This they shall give, every one that passeth among them that are numbered, half a shekel after the shekel of the sanctuary: (a shekel [is] twenty gerahs

an half shekel [shall be] the offering of the LORD.
Exd 30:14 Every one that passeth among them that are numbered, from twenty years old and above, shall give an offering unto the LORD.
Exd 30:15 The rich shall not give more, and the poor shall not give less than half a shekel, when [they] give an offering unto the LORD, to make an atonement for your souls.
He stated that the shekel of the sanctuary represented the tithe, and so therefore half of the tithe (an half shekel) should be given as an offering.