title: NCalc precision problems
body: <p>I got some rounding problems with NCalc.
  My problem is quite simple. just add 0.5 and 0.5555. 
  expected result is 1.0555. This i need to round to 3 fractions. 
  1.056</p>
  
  <p>float and double should not cause me any precision problems at a 5 digit number. However NCalc does.</p>
  
  <pre><code>Expression ex = new Expression("0.5 + 0.5555");
  object result = ex.Evaluate();
  
  result  1.0554999999999999  object {double}
  </code></pre>
  
  <p>This will round down instead of up. Even if the error is 0.0000000~~~~1. 
  Anyone have any ideas how I can solve this ?</p>