No because of a few things, you don't ever want to tune a guitar with a capo on it because the tension just isn't right and it could definately cause some broken strings a lot more so than without a capo, and the other reason is that if you had a capo on the first fret...that wouldn't do anything except raise every note up half a step.
Comments
find another F# and use your ear for it to tell you whether or not it is tuned as good as you can get it.
If you don't know what note the F# is...
In standard tuning, it would be the 2nd fret on either the first or sixth string
if in Open D or Drop-D it would be the 4th fret on the sixth string
hope that helps
-seth
I remember wondering the same thing with my old tuner
e|---|
B|---|
G|-0-|
D|-4-|
A|---|
E|---|
...at the same time until the notes sound the same (while tuning your G-sting down appropriately).