The logo was supposed to represent the American Bald Eagle overseeing the scales of justice in an effort to increase the morale and self-image of those who work there.
The Eagle symbolises America, which is holding even scales.
The Garland is associated with Caesar. I would guess that it comes from the famous biblical quote "Render unto Caesar the things that are Caesar's, and unto God the things that are God's" Which basically means that you have to pay your taxes.
So what its saying is. America has fair taxes that it is your Christian duty to pay.