Kill all terminals so they don't reappear
I'm no Terminal guru, however it appears to respond in the same way as any other app.  

If you quit it, then at next launch it will restore all previously open windows.
This is a global pref, set from System Prefs > General > Close windows when quitting an app.

If you don't want to change this pref globally, then the simplest solution would be to close the windows manually before Quit.

 Cmd ⌘   Opt ⌥   W  is the system-wide shortcut to do that.

As far as I'm aware, killall Terminal is the same as  Cmd ⌘   Q   in that respect, i.e. a 'polite' quit command.