Technically you're supposed to pay your state's tax, even for a purchase where you were physically in another state. Even if that other state actually charges its own sales tax!
IIRC you're expected to get the out of state retailer to reimburse you at a later time and then when you're paying your income taxes you include any purchases subject to use tax.
> Use Tax on the Difference
> If you paid at least 6 percent to another state on your purchase, you do not owe use tax to Michigan. If you paid less than 6 percent, you owe the difference.
> NOTE: The full 6 percent use tax is also owed on purchases made in a foreign country.
[1]: https://www.taxslayer.com/support/1153/michigan-use-tax
[2]: https://www.michigan.gov/documents/taxes/MI_1040_Instruction...
In Massachusetts, oddly, if you paid less than the Mass sales tax rate of 6.25%, you owe 6.25% use tax. It's not the delta you owe, it's the full amount. But you don't owe it at all if you paid more than the Mass rate.