Credit to youtuber Huu aka lunazian, check out his cover
of this song for some reference if you'd like: http://youtu.be/OJpj7Bkn77s
This is more of an acoustic version, anyways, same 5 chords throughout the song:

Em: 022000
Bm7:x24232 
Bbm7:x13121
Am7:x02010
C:  x32010
D6: x5403x (I think this one's called a D6, not sure)

[Intro]

Em, Bm7,Bbm7,Am7,C,D6

[Verse 1]

Em           Bm7
I know what you did

Am7    C D6
I know

        Em            Bm7
So I'ma let you taste hurt

                    Am7
I ain't washing my sins
 
                    C   D6
I ain't washing my sins

[Pre-Chorus]
                 Em
Now we're lying about the nights

                Bm7
Hiding it all behind the smiles

               Am7          C D6
Take a look at what you did

                                  Em
You probably thought that you'd break my heart
 
                                 Bm7
You probably thought that you'd make me cry

               Am7
But baby it's okay

              C  D6
I swear it's okay

[Chorus]

              Em                  Bm7
'Cause I know everything (eh eh eh eh)

       Am7        C D6
I know everything

       Em         Bm7
I know everything

       Am7        C D6
I know everything

[Bridge]

            Em                        Bm7
Now these talks don't twist like they did before

                      Am7
It's hard to keep you up

            C     D6
And you are crying

                  Em
But baby it don't hurt

             Bm7
Oh, like you thought it would 

     Am7                  C D6
The more of you the merrier

[Pre-Chorus]

                 Em
Now we're lying about the nights

                Bm7
Hiding it all behind the smiles

               Am7          C D6
Take a look at what you did

                                  Em
You probably thought that you'd break my heart
 
                                 Bm7
You probably thought that you'd make me cry

               Am7
But baby it's okay

              C  D6
I swear it's okay

[Chorus]

              Em                  Bm7
'Cause I know everything (eh eh eh eh)

       Am7        C D6
I know everything

       Em         Bm7
I know everything

       Am7        C D6
I know everything