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 $24.79   5.620%   $26.1832   $26.18   $26.20   $26.20  
  Purchase #2 $185.48   11.141%   $206.1443   $206.14   $206.15   $206.10  
  Purchase #3 $40.99   13.468%   $46.5105   $46.51   $46.50   $46.50  
  Purchase #4 $235.63   5.612%   $248.8536   $248.85   $248.85   $248.90  
  Purchase #5 $38.56   4.741%   $40.3881   $40.39   $40.40   $40.40  
  Purchase #6 $213.93   11.484%   $238.4977   $238.50   $238.50   $238.50  
  Purchase #7 $209.85   3.846%   $217.9208   $217.92   $217.90   $217.90  
  7 purchase totals = $949.23       $1,024.4982   $1,024.49   $1,024.50   $1,024.50