Here's a nice and easy way to play it.
Intro
C C/G G Am Am/G F C G
Verse
C C/G G Am Am/G F
Well it ain't no use to sit and wonder why, babe,
C G G6 G
If'n you don't know by now.
C C/G G Am Am/G D7/F#
It ain't no use to sit and wonder why, babe.
G G6 G7
It'll never do, somehow.
C C7
When the rooster crows at the break of dawn
F D7/F#
look out your window and I'll be gone
C C/B Am Am/G F
You're the reason I'm travelin' on,
C G G6 C
but don't think twice, it's al-right.
The lyrics are Bob Dylan's, but the music is a traditional song.