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 $239.77   9.523%   $262.6033   $262.60   $262.60   $262.60  
  Purchase #2 $217.27   6.594%   $231.5968   $231.60   $231.60   $231.60  
  Purchase #3 $101.73   10.793%   $112.7097   $112.71   $112.70   $112.70  
  Purchase #4 $41.70   10.857%   $46.2274   $46.23   $46.25   $46.20  
  Purchase #5 $101.73   7.162%   $109.0159   $109.02   $109.00   $109.00  
  Purchase #6 $152.84   9.581%   $167.4836   $167.48   $167.50   $167.50  
  Purchase #7 $213.97   6.133%   $227.0928   $227.09   $227.10   $227.10  
  7 purchase totals = $1,069.01       $1,156.7295   $1,156.73   $1,156.75   $1,156.70