mT Rushmore RV park recommendation?

I got tagged with a $15/vehicle fee just to drive through Custer because google maps routed me there and the road runs right through the park - however, if I was camping, I would stay at Custer. Nice wildlife with buffalo and pronghorns. Also, Wind Cave National Park is south of Custer, which was our destination as we drove from Rushmore. Wind Cave is a neat phenomenon and worth a day if you are in the area. We were actually more impressed with it than Rushmore, but we didn't have time to do hikes at Rushmore due to our itinerary.