Are hotel-motel taxes unconstitutional?

Taxation is a form of regulation. The interstate clause of the U.S. Consttitution (Article l, section 8) authorizes Congress to regulate interstate commerce. Since hotels and motels do business with interstate travelers they are involvel in interstate commerce. Hotel-motel taxes are levied by towns and cities rather than by Congress; thus the lattter are regulating interstate commerce. Is this unconstitutional?