Yes it is compatible with the ryzen 5 3600 considering it's big bro the 3600X works just fine. These cpu have the same architecture and work great with a b450. And its not just these cpus that work with a b450. If your cpu is am4 it will work.

Does B450 Tomahawk support Ryzen 5 3600?

So long as you're on the latest BIOS update for that board, that enables use of Ryzen 3000 series chips, yes you should be good to go!

Does the B450 Tomahawk support Ryzen 3000?

Yes, the Max series is compatible out of the box with ryzen 3000, as well as supporting 2000. There is just a larger bios chip than the non Max version of those boards.