One needs to be a bit careful in this area, because sometimes a song that appears to end on a note other than the tonic might actually be modal.
One example is "The Great Silkie (Selchie) of Sule Skerry," the version sung by Joan Baez. It's in mixolydian mode. This mode is the same as a major scale, except that it has a flatted seventh. I think Joan does it in D – which is to say, like a D major scale with a C natural instead of a C#. The chords would be D (as the tonic chord), G (subdominant), and C (as the dominant rather than A), with Bm, Em, and Am also available whenever appropriate. So examining the chord structure, it seems to start and end on the dominant, but not so. I does end on the tonic—of the mixolydian mode.