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 $193.25   9.175%   $210.9807   $210.98   $211.00   $211.00  
  Purchase #2 $26.81   11.277%   $29.8334   $29.83   $29.85   $29.80  
  Purchase #3 $235.42   3.109%   $242.7392   $242.74   $242.75   $242.70  
  Purchase #4 $68.69   5.193%   $72.2571   $72.26   $72.25   $72.30  
  Purchase #5 $154.31   6.485%   $164.317   $164.32   $164.30   $164.30  
  Purchase #6 $101.53   4.168%   $105.7618   $105.76   $105.75   $105.80  
  Purchase #7 $32.88   11.545%   $36.676   $36.68   $36.70   $36.70  
  7 purchase totals = $812.89       $862.5652   $862.57   $862.60   $862.60