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 $69.90   3.220%   $72.1508   $72.15   $72.15   $72.20  
  Purchase #2 $238.99   9.433%   $261.5339   $261.53   $261.55   $261.50  
  Purchase #3 $186.65   4.825%   $195.6559   $195.66   $195.65   $195.70  
  Purchase #4 $61.60   4.441%   $64.3357   $64.34   $64.35   $64.30  
  Purchase #5 $47.53   12.810%   $53.6186   $53.62   $53.60   $53.60  
  Purchase #6 $147.95   6.621%   $157.7458   $157.75   $157.75   $157.70  
  Purchase #7 $124.70   10.616%   $137.9382   $137.94   $137.95   $137.90  
  7 purchase totals = $877.32       $942.9789   $942.99   $943.00   $942.90