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 $105.96   5.660%   $111.9573   $111.96   $111.95   $112.00  
  Purchase #2 $141.92   7.336%   $152.3313   $152.33   $152.35   $152.30  
  Purchase #3 $109.32   6.338%   $116.2487   $116.25   $116.25   $116.20  
  Purchase #4 $73.61   4.217%   $76.7141   $76.71   $76.70   $76.70  
  Purchase #5 $236.70   9.486%   $259.1534   $259.15   $259.15   $259.20  
  Purchase #6 $196.40   3.369%   $203.0167   $203.02   $203.00   $203.00  
  Purchase #7 $241.76   7.680%   $260.3272   $260.33   $260.35   $260.30  
  7 purchase totals = $1,105.67       $1,179.7487   $1,179.75   $1,179.75   $1,179.70