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 $180.66   8.306%   $195.6656   $195.67   $195.65   $195.70  
  Purchase #2 $177.86   10.208%   $196.0159   $196.02   $196.00   $196.00  
  Purchase #3 $146.46   8.674%   $159.1639   $159.16   $159.15   $159.20  
  Purchase #4 $239.27   13.502%   $271.5762   $271.58   $271.60   $271.60  
  Purchase #5 $242.75   3.492%   $251.2268   $251.23   $251.25   $251.20  
  Purchase #6 $234.61   11.509%   $261.6113   $261.61   $261.60   $261.60  
  Purchase #7 $35.70   3.587%   $36.9806   $36.98   $37.00   $37.00  
  7 purchase totals = $1,257.31       $1,372.2403   $1,372.25   $1,372.25   $1,372.30