Sales tax regarding the cash for clunkers program

I own an auto salvage yard and went through the cars.gov website and cannot for the life of me find out where to register my company to purchase these junked cars.....I found the list of other salvage yards but...

Does Pennsylvania collect sales tax on the price of gasoline purchased at the pumP

Would designing and maintaining web sites be subject to Ohio sales tax?

If my boss has not paid the sales taxes in awhile would that hold up my tax return? Even if they take the money out of my pay check

Sales billed before the hike in sales tax. Customers have paid part of the amount due before the hike. What about the remaining portion that they owe that will be paid after the rate hike? (Went from 6% to 6.5%...