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 $211.73   12.194%   $237.5484   $237.55   $237.55   $237.50  
  Purchase #2 $224.34   9.716%   $246.1369   $246.14   $246.15   $246.10  
  Purchase #3 $57.53   7.857%   $62.0501   $62.05   $62.05   $62.10  
  Purchase #4 $68.36   11.506%   $76.2255   $76.23   $76.25   $76.20  
  Purchase #5 $69.61   11.856%   $77.863   $77.86   $77.85   $77.90  
  Purchase #6 $222.71   9.796%   $244.5267   $244.53   $244.55   $244.50  
  Purchase #7 $7.56   9.758%   $8.2977   $8.30   $8.30   $8.30  
  7 purchase totals = $861.84       $952.6483   $952.66   $952.70   $952.60