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 $243.47   7.859%   $262.6043   $262.60   $262.60   $262.60  
  Purchase #2 $84.39   12.578%   $95.0046   $95.00   $95.00   $95.00  
  Purchase #3 $143.61   4.204%   $149.6474   $149.65   $149.65   $149.60  
  Purchase #4 $71.86   11.191%   $79.9019   $79.90   $79.90   $79.90  
  Purchase #5 $205.40   5.303%   $216.2924   $216.29   $216.30   $216.30  
  Purchase #6 $237.28   5.109%   $249.4026   $249.40   $249.40   $249.40  
  Purchase #7 $241.77   12.177%   $271.2103   $271.21   $271.20   $271.20  
  7 purchase totals = $1,227.78       $1,324.0635   $1,324.05   $1,324.05   $1,324.00