"one or more rounds"

[Killer Angel]

I think that it depends on the spell - I'd agree with you for antimagic field, but I'd think that for something like Zone of Truth where each individual affected gets their own will save, you could end it (applying only to you, not to the whole area) with IHS.
Anyway, I found an official ruling.
It cannot remove instantaneous effects, but is not otherwise limited by how the duration is measured (including permanent)

Yep, the "including permanent-duration spells or effects" is pretty clear, and resolves the OP's doubt on round duration.
Also, I agree on ZoT