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 $114.59   11.406%   $127.6601   $127.66   $127.65   $127.70  
  Purchase #2 $206.97   3.258%   $213.7131   $213.71   $213.70   $213.70  
  Purchase #3 $178.42   9.496%   $195.3628   $195.36   $195.35   $195.40  
  Purchase #4 $231.88   3.162%   $239.212   $239.21   $239.20   $239.20  
  Purchase #5 $23.94   3.847%   $24.861   $24.86   $24.85   $24.90  
  Purchase #6 $248.28   7.235%   $266.2431   $266.24   $266.25   $266.20  
  Purchase #7 $179.38   10.143%   $197.5745   $197.57   $197.55   $197.60  
  7 purchase totals = $1,183.46       $1,264.6266   $1,264.61   $1,264.55   $1,264.70