I worked at a Sears Auto Center for a while in college (about 7 years ago).
There was a Super Walmart a couple blocks away. They sold lawn and garden tires, but wouldn't mount them. We had people come in all the time with lawn tires that they bought at Walmart, and Walmart evidently told them we could mount them.
We didn't really have any special tools for it, other than a threaded post welded to a table to hold the wheel. Walmart should have been able to do it, but they wouldn't, for some reason.
Their policy may have changed, but that was the case with the store in my area at that time.