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 $103.84   10.267%   $114.5013   $114.50   $114.50   $114.50  
  Purchase #2 $196.64   5.639%   $207.7285   $207.73   $207.75   $207.70  
  Purchase #3 $43.79   3.508%   $45.3262   $45.33   $45.35   $45.30  
  Purchase #4 $63.68   11.248%   $70.8427   $70.84   $70.85   $70.80  
  Purchase #5 $41.53   10.860%   $46.0402   $46.04   $46.05   $46.00  
  Purchase #6 $117.67   11.709%   $131.448   $131.45   $131.45   $131.40  
  Purchase #7 $34.84   9.129%   $38.0205   $38.02   $38.00   $38.00  
  7 purchase totals = $601.99       $653.9074   $653.91   $653.95   $653.70