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 $60.41   4.542%   $63.1538   $63.15   $63.15   $63.20  
  Purchase #2 $109.73   4.759%   $114.9521   $114.95   $114.95   $115.00  
  Purchase #3 $106.54   7.370%   $114.392   $114.39   $114.40   $114.40  
  Purchase #4 $200.46   8.480%   $217.459   $217.46   $217.45   $217.50  
  Purchase #5 $195.29   8.535%   $211.958   $211.96   $211.95   $212.00  
  Purchase #6 $127.78   3.279%   $131.9699   $131.97   $131.95   $132.00  
  Purchase #7 $122.43   8.304%   $132.5966   $132.60   $132.60   $132.60  
  7 purchase totals = $922.64       $986.4814   $986.48   $986.45   $986.70