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 $207.55   3.612%   $215.0467   $215.05   $215.05   $215.00  
  Purchase #2 $42.33   13.856%   $48.1952   $48.20   $48.20   $48.20  
  Purchase #3 $137.36   7.217%   $147.2733   $147.27   $147.25   $147.30  
  Purchase #4 $24.63   7.169%   $26.3957   $26.40   $26.40   $26.40  
  Purchase #5 $149.46   13.138%   $169.0961   $169.10   $169.10   $169.10  
  Purchase #6 $215.34   13.595%   $244.6155   $244.62   $244.60   $244.60  
  Purchase #7 $168.29   8.390%   $182.4095   $182.41   $182.40   $182.40  
  7 purchase totals = $944.96       $1,033.0320   $1,033.05   $1,033.00   $1,033.00