Addition or Substraction of Double Values in Java

In subtracting one double from another, namely 45.32 - 45.31, I get a
result of 0.00999999999999801. According to all the math I've ever 
learned, the answer should be .01. Now the answer is:

double x = 45.32;

double y = 45.31;

double answer = (x - y);

answer = Math.round(answer*100)/100.0d;