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 $62.50   11.621%   $69.7631   $69.76   $69.75   $69.80  
  Purchase #2 $102.87   13.194%   $116.4427   $116.44   $116.45   $116.40  
  Purchase #3 $234.99   5.664%   $248.2998   $248.30   $248.30   $248.30  
  Purchase #4 $209.94   10.821%   $232.6576   $232.66   $232.65   $232.70  
  Purchase #5 $34.27   11.452%   $38.1946   $38.19   $38.20   $38.20  
  Purchase #6 $27.73   9.684%   $30.4154   $30.42   $30.40   $30.40  
  Purchase #7 $190.60   10.683%   $210.9618   $210.96   $210.95   $211.00  
  7 purchase totals = $862.90       $946.7350   $946.73   $946.70   $946.80