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 $244.26   10.227%   $269.2405   $269.24   $269.25   $269.20  
  Purchase #2 $157.61   10.622%   $174.3513   $174.35   $174.35   $174.40  
  Purchase #3 $41.64   6.776%   $44.4615   $44.46   $44.45   $44.50  
  Purchase #4 $189.78   6.496%   $202.1081   $202.11   $202.10   $202.10  
  Purchase #5 $216.48   4.396%   $225.9965   $226.00   $226.00   $226.00  
  Purchase #6 $231.38   9.240%   $252.7595   $252.76   $252.75   $252.80  
  Purchase #7 $242.88   7.761%   $261.7299   $261.73   $261.75   $261.70  
  7 purchase totals = $1,324.03       $1,430.6473   $1,430.65   $1,430.65   $1,430.70