code: function roundHalfDown(num, precision) {
      var multiplier = pow(10, precision);
      return Math.floor(num * multiplier) / multiplier;
  }
docs: Rounds a number half down to the specified places.
  @example
  
  comb.number.roundHalfDown(0.225, 2);     //0.22
  comb.number.roundHalfDown(10.384, 2);    //10.38
  comb.number.roundHalfDown(10.386, 2);    //10.38
  comb.number.roundHalfDown(10.3869, 3);   //10.386
  comb.number.roundHalfDown(10.3861, 3);   //10.386
  comb.number.roundHalfDown(10.269019, 5); //10.26901
  
  @param {Number} num the number to round.
  @param {Number} precision the number of places to round to.
  @static
  @memberOf comb.number