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 $107.86   5.660%   $113.9649   $113.96   $113.95   $114.00  
  Purchase #2 $183.68   6.857%   $196.2749   $196.27   $196.25   $196.30  
  Purchase #3 $88.63   4.559%   $92.6706   $92.67   $92.65   $92.70  
  Purchase #4 $207.80   9.232%   $226.9841   $226.98   $227.00   $227.00  
  Purchase #5 $146.56   3.428%   $151.5841   $151.58   $151.60   $151.60  
  Purchase #6 $69.81   5.275%   $73.4925   $73.49   $73.50   $73.50  
  Purchase #7 $68.35   11.473%   $76.1918   $76.19   $76.20   $76.20  
  7 purchase totals = $872.69       $931.1629   $931.14   $931.15   $931.30