The SCOTUS did not approve a “mandate tax”
They simply ruled that it was a tax...one of the big arguments in the case was if the mandate was a penalty or a tax.
The SCOTUS simply ruled that it was a tax. They are prohibited from making a ruling on the Consitutionality of the tax by the Anti-Injunction Act until the tax is actually imposed (which will be in 2014).
They kicked the can down the road.