Depending on the conditions, you may be required to have an 1) SUV, 2) an SUV with snow tires, or 3) chains. The Highway Patrol puts up road blocks and they won't let you proceed without the required equipment.
At these road stops, there are entrepreneurs along the road who rent and install chains. This is the easiest way to go.
Another option is to stop at Wal-mart and buy the right chains on the way up, leave them in the box, and then return them on your way down the hill if you don't need them. Rental car agencies don't usually provide chains because of the danger of damaging the car with improperly installed chains.
Although we haven't had great snow this year, road closures are very common in the Tahoe area during the winter, especially going over the pass to reach Tahoe. I would definitely rent a 4WD SUV with snow tires for a ski trip.
More info. -
http://www.dot.ca.gov/hq/roadinfo/chcontrl.htm