Just found this in Mathematica 7.0 for Mac OS X x86 (64-bit) (November 11, 2008):

x=Exp[Pi Sqrt[163] ];
N[x-Round[x] ]
N[x-Floor[x] ]
N[x-Ceiling[x] ]
N[x - Round[x], 2]
N[x - Floor[x], 2]
N[x - Ceiling[x], 2]


The functions Round, Floor, and Ceiling are the obvious functions, while "N" converts the infinite-precision expression to a floating point number (the last three lines are aimed at 2-digit precision, while the first three should be 16-digit).

The first three calculations turn up as "-480." The last three give more correct values of -$7.5*10^{-13}, 1.0, -7.5*10^{-13}$.