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 $56.61   9.532%   $62.0061   $62.01   $62.00   $62.00  
  Purchase #2 $114.88   13.597%   $130.5002   $130.50   $130.50   $130.50  
  Purchase #3 $147.75   10.632%   $163.4588   $163.46   $163.45   $163.50  
  Purchase #4 $55.30   10.679%   $61.2055   $61.21   $61.20   $61.20  
  Purchase #5 $173.93   5.113%   $182.823   $182.82   $182.80   $182.80  
  Purchase #6 $135.43   3.728%   $140.4788   $140.48   $140.50   $140.50  
  Purchase #7 $188.36   9.439%   $206.1393   $206.14   $206.15   $206.10  
  7 purchase totals = $872.26       $946.6117   $946.62   $946.60   $946.60