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 $228.35   4.200%   $237.9407   $237.94   $237.95   $237.90  
  Purchase #2 $248.39   8.203%   $268.7654   $268.77   $268.75   $268.80  
  Purchase #3 $224.59   9.296%   $245.4679   $245.47   $245.45   $245.50  
  Purchase #4 $227.39   13.195%   $257.3941   $257.39   $257.40   $257.40  
  Purchase #5 $85.32   12.833%   $96.2691   $96.27   $96.25   $96.30  
  Purchase #6 $104.74   10.149%   $115.3701   $115.37   $115.35   $115.40  
  Purchase #7 $133.47   6.105%   $141.6183   $141.62   $141.60   $141.60  
  7 purchase totals = $1,252.25       $1,362.8256   $1,362.83   $1,362.75   $1,362.90