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 $117.89   6.824%   $125.9348   $125.93   $125.95   $125.90  
  Purchase #2 $107.92   11.853%   $120.7118   $120.71   $120.70   $120.70  
  Purchase #3 $194.81   7.263%   $208.9591   $208.96   $208.95   $209.00  
  Purchase #4 $230.64   10.567%   $255.0117   $255.01   $255.00   $255.00  
  Purchase #5 $55.52   3.696%   $57.572   $57.57   $57.55   $57.60  
  Purchase #6 $48.46   10.634%   $53.6132   $53.61   $53.60   $53.60  
  Purchase #7 $120.51   10.356%   $132.99   $132.99   $133.00   $133.00  
  7 purchase totals = $875.75       $954.7926   $954.78   $954.75   $954.80