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 $248.38   5.723%   $262.5948   $262.59   $262.60   $262.60  
  Purchase #2 $162.59   13.321%   $184.2486   $184.25   $184.25   $184.20  
  Purchase #3 $224.80   8.822%   $244.6319   $244.63   $244.65   $244.60  
  Purchase #4 $179.84   3.258%   $185.6992   $185.70   $185.70   $185.70  
  Purchase #5 $221.28   4.656%   $231.5828   $231.58   $231.60   $231.60  
  Purchase #6 $73.56   6.247%   $78.1553   $78.16   $78.15   $78.20  
  Purchase #7 $234.49   10.765%   $259.7328   $259.73   $259.75   $259.70  
  7 purchase totals = $1,344.94       $1,446.6454   $1,446.64   $1,446.70   $1,446.60