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 $141.86   8.523%   $153.9507   $153.95   $153.95   $154.00  
  Purchase #2 $129.56   8.335%   $140.3588   $140.36   $140.35   $140.40  
  Purchase #3 $164.92   7.289%   $176.941   $176.94   $176.95   $176.90  
  Purchase #4 $76.73   12.423%   $86.2622   $86.26   $86.25   $86.30  
  Purchase #5 $25.63   7.863%   $27.6453   $27.65   $27.65   $27.60  
  Purchase #6 $24.62   4.379%   $25.6981   $25.70   $25.70   $25.70  
  Purchase #7 $153.35   12.622%   $172.7058   $172.71   $172.70   $172.70  
  7 purchase totals = $716.67       $783.5619   $783.57   $783.55   $783.60