Well there are three types of tons.
The Short ton, the Long ton, and the Tonne.
The short ton is 2000 pounds (advp) (lb), or 2430.5556960 pounds (troy).
The Long ton is 2240 pounds (advp) (lb), or 2722.222380 pounds (troy).
The Tonne is the metric form, and is 2204.6226220 pounds (advp) (lb), or 2679.2290360 pounds (troy).
Assuming that you are talking about the short ton, and the form of pound you're using is the (lb). 555 pounds would equal 0.2775 Short tons.