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 $59.60   10.317%   $65.7489   $65.75   $65.75   $65.70  
  Purchase #2 $179.48   7.326%   $192.6287   $192.63   $192.65   $192.60  
  Purchase #3 $203.95   5.544%   $215.257   $215.26   $215.25   $215.30  
  Purchase #4 $232.74   10.849%   $257.99   $257.99   $258.00   $258.00  
  Purchase #5 $175.78   4.138%   $183.0538   $183.05   $183.05   $183.10  
  Purchase #6 $157.66   11.617%   $175.9754   $175.98   $176.00   $176.00  
  Purchase #7 $195.76   13.870%   $222.9119   $222.91   $222.90   $222.90  
  7 purchase totals = $1,204.97       $1,313.5657   $1,313.57   $1,313.60   $1,313.60