Michael is right, though he did cut some corners.
A perfect answer would use the actual Earth-Pluto distance as of today, Dec. 1, which happens to be 2,959,134,444 miles. Thus, a round trip would cover 5,918,268,888 miles. The number of miles driven by Wisconsinites in 2003 (which Michael does have correct) is almost exactly 10 times this distance.
(If you want to drive to Pluto you'd better hurry; tomorrow it will be 350,000 miles further away....)
For any other geeky engineer types out there: http://ephemeral.info/tru/