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 $213.33   11.397%   $237.6432   $237.64   $237.65   $237.60  
  Purchase #2 $11.71   11.554%   $13.063   $13.06   $13.05   $13.10  
  Purchase #3 $60.54   9.863%   $66.5111   $66.51   $66.50   $66.50  
  Purchase #4 $114.63   11.312%   $127.5969   $127.60   $127.60   $127.60  
  Purchase #5 $234.77   5.211%   $247.0039   $247.00   $247.00   $247.00  
  Purchase #6 $119.98   5.724%   $126.8477   $126.85   $126.85   $126.80  
  Purchase #7 $94.73   7.231%   $101.5799   $101.58   $101.60   $101.60  
  7 purchase totals = $849.69       $920.2457   $920.24   $920.25   $920.20