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 $216.68   10.542%   $239.5224   $239.52   $239.50   $239.50  
  Purchase #2 $211.53   7.146%   $226.6459   $226.65   $226.65   $226.60  
  Purchase #3 $246.32   11.206%   $273.9226   $273.92   $273.90   $273.90  
  Purchase #4 $190.43   11.254%   $211.861   $211.86   $211.85   $211.90  
  Purchase #5 $70.76   3.189%   $73.0165   $73.02   $73.00   $73.00  
  Purchase #6 $233.99   11.785%   $261.5657   $261.57   $261.55   $261.60  
  Purchase #7 $177.61   10.463%   $196.1933   $196.19   $196.20   $196.20  
  7 purchase totals = $1,347.32       $1,482.7274   $1,482.73   $1,482.65   $1,482.70