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 $57.53   7.690%   $61.9541   $61.95   $61.95   $62.00  
  Purchase #2 $59.42   12.344%   $66.7548   $66.75   $66.75   $66.80  
  Purchase #3 $56.93   6.298%   $60.5155   $60.52   $60.50   $60.50  
  Purchase #4 $218.86   3.850%   $227.2861   $227.29   $227.30   $227.30  
  Purchase #5 $231.77   12.594%   $260.9591   $260.96   $260.95   $261.00  
  Purchase #6 $122.74   13.615%   $139.4511   $139.45   $139.45   $139.50  
  Purchase #7 $140.36   7.319%   $150.6329   $150.63   $150.65   $150.60  
  7 purchase totals = $887.61       $967.5536   $967.55   $967.55   $967.70