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 $60.54   3.608%   $62.7243   $62.72   $62.70   $62.70  
  Purchase #2 $63.77   12.414%   $71.6864   $71.69   $71.70   $71.70  
  Purchase #3 $59.39   10.421%   $65.579   $65.58   $65.60   $65.60  
  Purchase #4 $176.76   6.859%   $188.884   $188.88   $188.90   $188.90  
  Purchase #5 $69.46   11.800%   $77.6563   $77.66   $77.65   $77.70  
  Purchase #6 $158.55   12.407%   $178.2213   $178.22   $178.20   $178.20  
  Purchase #7 $109.94   11.326%   $122.3918   $122.39   $122.40   $122.40  
  7 purchase totals = $698.41       $767.1431   $767.14   $767.15   $767.20