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 $222.78   10.642%   $246.4882   $246.49   $246.50   $246.50  
  Purchase #2 $56.61   13.301%   $64.1397   $64.14   $64.15   $64.10  
  Purchase #3 $219.73   7.754%   $236.7679   $236.77   $236.75   $236.80  
  Purchase #4 $168.49   7.387%   $180.9364   $180.94   $180.95   $180.90  
  Purchase #5 $47.49   6.302%   $50.4828   $50.48   $50.50   $50.50  
  Purchase #6 $166.26   6.150%   $176.485   $176.49   $176.50   $176.50  
  Purchase #7 $188.49   10.683%   $208.6264   $208.63   $208.65   $208.60  
  7 purchase totals = $1,069.85       $1,163.9264   $1,163.94   $1,164.00   $1,163.90