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 $60.31   3.831%   $62.6205   $62.62   $62.60   $62.60  
  Purchase #2 $192.43   12.847%   $217.1515   $217.15   $217.15   $217.20  
  Purchase #3 $9.77   12.552%   $10.9963   $11.00   $11.00   $11.00  
  Purchase #4 $235.67   8.359%   $255.3697   $255.37   $255.35   $255.40  
  Purchase #5 $127.25   13.792%   $144.8003   $144.80   $144.80   $144.80  
  Purchase #6 $58.27   9.704%   $63.9245   $63.92   $63.90   $63.90  
  Purchase #7 $82.94   5.316%   $87.3491   $87.35   $87.35   $87.30  
  7 purchase totals = $766.64       $842.2119   $842.21   $842.15   $842.20