If you apply for a sales tax exemption permit, you will be asked to provide your monthly sales, estimated or actual.  What this information will be used for is not explained, but I will tell you.
Every quarter, you will receive a freaking BILL from the state for sales tax and it is based on this figure.  So if you put-down that your estimated monthly sales will be $10,000, and the sales tax rate is 6%, you will get a freaking quarterly BILL for $1800.
The state is always pleased to get more revenue than it expected, but it hates to get less than expected.  So if your monthly sales are actually $1000, prepare to justify to the State of Michigan why you only sent them $180 instead of the $1800 you 'promised' to pay.  I learned this the hard way.
I had no idea what my sales would be, because I had not actually started my business yet, nor the reason I was being asked.  So I just put down some number that I made up, figuring it was just something they always ask.  I think I put down $10,000 per month estimated sales.
I didn't have $10,000 in sales the first six months combined, but the State of Michigan sent me that $1800 bill like clockwork every quarter, and of course I had to file additional forms explaining why I was sending them something significantly less than $1800.
So if you apply for a sales tax license, put down some low-ball figure like $500 per month estimated sales.