Each one of us has a financial relationship with the Federal Government, where some money is paid and received by both parties. When you engage in certain acts of commerce (e.g. buying a house), the net amount of money exchanged between you and Federal Government moves slightly in your favor, i.e., you get a tax deduction. The impact of the Individual Mandate provision of the ACA is that a citizen must pay money (i.e. a fine) to the Federal Government if they have not purchased a health insurance policy. So, the net amount of money exchanged between that citizen and the Federal Government moves slightly in the Government's favor.
Since there is no substantive difference between paying a non-criminal fine and not being able to take a tax deduction, arguments for the Individual Mandate's lack of precedent are weak -- a matter of terminology rather than substance.