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 $239.42   9.427%   $261.9901   $261.99   $262.00   $262.00  
  Purchase #2 $134.86   6.781%   $144.0049   $144.00   $144.00   $144.00  
  Purchase #3 $161.93   3.660%   $167.8566   $167.86   $167.85   $167.90  
  Purchase #4 $47.92   6.625%   $51.0947   $51.09   $51.10   $51.10  
  Purchase #5 $201.76   6.145%   $214.1582   $214.16   $214.15   $214.20  
  Purchase #6 $120.94   7.668%   $130.2137   $130.21   $130.20   $130.20  
  Purchase #7 $61.91   4.602%   $64.7591   $64.76   $64.75   $64.80  
  7 purchase totals = $968.74       $1,034.0773   $1,034.07   $1,034.05   $1,034.20