Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $194.42   3.863%   $201.9304   $201.93   $201.95   $201.90  
  Purchase #2 $247.27   9.623%   $271.0648   $271.06   $271.05   $271.10  
  Purchase #3 $140.83   4.242%   $146.804   $146.80   $146.80   $146.80  
  Purchase #4 $234.73   11.466%   $261.6441   $261.64   $261.65   $261.60  
  Purchase #5 $71.89   5.578%   $75.9   $75.90   $75.90   $75.90  
  Purchase #6 $50.29   11.637%   $56.1422   $56.14   $56.15   $56.10  
  Purchase #7 $106.55   11.746%   $119.0654   $119.07   $119.05   $119.10  
  7 purchase totals = $1,045.98       $1,132.5509   $1,132.54   $1,132.55   $1,132.50