All in all, i spend 10 weekends a year in tahoe and dont own chains. If you don't have a lot of snow driving experience it couldnt hurt, but definitely not mandatory
which way are you going? The path through south lake via 50 is never too bad, and depending on when you go, you will probably be in traffic and have no problems. Sierra snow (being as heavy as it is) isn't too bad to drive in
highway 80 on the north lake route is usually pretty clear, but some of the roads to various ski areas can get pretty icy, but they do a good job of keeping the roads clear.