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 $216.90   7.622%   $233.4321   $233.43   $233.45   $233.40  
  Purchase #2 $247.74   5.655%   $261.7497   $261.75   $261.75   $261.70  
  Purchase #3 $164.98   12.257%   $185.2016   $185.20   $185.20   $185.20  
  Purchase #4 $19.55   3.148%   $20.1654   $20.17   $20.15   $20.20  
  Purchase #5 $242.93   3.477%   $251.3767   $251.38   $251.40   $251.40  
  Purchase #6 $44.53   4.720%   $46.6318   $46.63   $46.65   $46.60  
  Purchase #7 $228.91   3.173%   $236.1733   $236.17   $236.15   $236.20  
  7 purchase totals = $1,165.54       $1,234.7306   $1,234.73   $1,234.75   $1,234.70