Yes, someone in New Jersey actually bought Hitler's car. Well, one of the many cars they used to drive Hitler around in. How special is it? Probably special enough to be worth a million and a half dollars, apparently. Still, I would guess that there were numerous cars that were used during that era, many of them kept in different locations.
I last visited the Mercedes Benz Museum in Stuttgart in 2011. There is a timeline that appears on the walls as you start at the top floor and wind your way down. This is what the inside looks like:
I don't remember any of the Nazi-era cars on display, and I know I was paying attention when we moved through that part of the museum, but that is actually changing:
I wouldn't expect them to "celebrate" the fact that they custom manufactured a lot of Nazi-era vehicles (with slave labor, to boot) but at least they do acknowledge their history.