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 $62.64   11.152%   $69.6256   $69.63   $69.65   $69.60  
  Purchase #2 $66.43   10.553%   $73.4404   $73.44   $73.45   $73.40  
  Purchase #3 $40.98   10.504%   $45.2845   $45.28   $45.30   $45.30  
  Purchase #4 $221.60   11.198%   $246.4148   $246.41   $246.40   $246.40  
  Purchase #5 $104.38   11.575%   $116.462   $116.46   $116.45   $116.50  
  Purchase #6 $146.52   7.122%   $156.9552   $156.96   $156.95   $157.00  
  Purchase #7 $51.58   3.508%   $53.3894   $53.39   $53.40   $53.40  
  7 purchase totals = $694.13       $761.5719   $761.57   $761.60   $761.60