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 $94.45   4.324%   $98.534   $98.53   $98.55   $98.50  
  Purchase #2 $14.42   5.308%   $15.1854   $15.19   $15.20   $15.20  
  Purchase #3 $148.56   6.110%   $157.637   $157.64   $157.65   $157.60  
  Purchase #4 $227.71   3.773%   $236.3015   $236.30   $236.30   $236.30  
  Purchase #5 $199.98   4.859%   $209.697   $209.70   $209.70   $209.70  
  Purchase #6 $64.66   4.303%   $67.4423   $67.44   $67.45   $67.40  
  Purchase #7 $133.99   5.484%   $141.338   $141.34   $141.35   $141.30  
  7 purchase totals = $883.77       $926.1352   $926.14   $926.20   $926.00