You'll have to pay sales tax somewhere. Each state has its own tax rules. Generally the key question is "When does title pass from the dealer to buyer?" If you buy the tractor out of state (Indiana) and pick it up there at the dealer, you'll likely have to pay Indiana taxes. But if the dealer delivered the tractor to you in Michigan, title would normally pass when the dealer delivers the equipment and Michigan taxes would be due. Although he likely will not charge you sales tax, you would still be personally liable. Either way, some taxes are due.
In NC and other states, you may be eligible for a reduced rate. In NC, for example, if the unit is used for farming production, the tax is only 1% with an $80.00 maximum. You'll need to see if your state has special rates and possibly you may qualify for them.
Good luck.