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 $43.81   8.625%   $47.5886   $47.59   $47.60   $47.60  
  Purchase #2 $106.72   11.673%   $119.1774   $119.18   $119.20   $119.20  
  Purchase #3 $218.48   10.719%   $241.8989   $241.90   $241.90   $241.90  
  Purchase #4 $96.54   8.112%   $104.3713   $104.37   $104.35   $104.40  
  Purchase #5 $46.44   11.390%   $51.7295   $51.73   $51.75   $51.70  
  Purchase #6 $56.83   13.514%   $64.51   $64.51   $64.50   $64.50  
  Purchase #7 $157.99   5.671%   $166.9496   $166.95   $166.95   $166.90  
  7 purchase totals = $726.81       $796.2253   $796.23   $796.25   $796.20