At this time, Dynamic Ship integrates with the EasyPost api. You can view a list of carriers supported by EasyPost here: https://www.easypost.com/carriers
TNT is considered an LTL and is not supported by EasyPost. Dynamic Ship does allow users to customize rate tables to include LTL carrier rates.
Dynamic Ship will be introducing live rate shopping for LTL in an upcoming version of the app. Please check back.