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 $68.63   10.738%   $75.9995   $76.00   $76.00   $76.00  
  Purchase #2 $89.63   8.676%   $97.4063   $97.41   $97.40   $97.40  
  Purchase #3 $145.65   4.348%   $151.9829   $151.98   $152.00   $152.00  
  Purchase #4 $89.30   5.195%   $93.9391   $93.94   $93.95   $93.90  
  Purchase #5 $239.63   6.605%   $255.4576   $255.46   $255.45   $255.50  
  Purchase #6 $229.69   6.105%   $243.7126   $243.71   $243.70   $243.70  
  Purchase #7 $44.26   10.716%   $49.0029   $49.00   $49.00   $49.00  
  7 purchase totals = $906.79       $967.5009   $967.50   $967.50   $967.50