Donald Trump is a sleazy business man and most of those guys who do all that big deal and trading stuff do not like to pay taxes. They are greedy and they know how to cheat the system. They are no better than a person who cheats the welfare system. They are all stealing money from the government.
Tax evasion is a pretty common practice among America's rich. There are a number of ways in order to protect your income that may include but not limited to: lying about your income, transferring your money to a safe location, have your family members control some of your income, etc. As someone who tries to build a multi-million dollar empire very quick these tactics seem essential, and there is no doubt that Donald Trump feels the same way considering the schemes he performed that are out in the open.
There is no evidence that Donald Trump has ever cheated on his taxes. It is not uncommon for extremely wealthy individuals to be audited by the IRS. However, Trump probably does take advantage of every legal tax deduction and loophole to minimize his tax burden. In short, just because Trump is audited by the IRS is does not mean that he has actually cheated on his taxes.
It still remains to be seen, but I don't believe Donald Trump cheats on his taxes, though I do believe that he does have a wealth of resources to help him take advantages of tax loopholes that allow him to pay far less taxes than he really should. This, by definition is not cheating, but working a broken system.