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 $247.56   5.822%   $261.9729   $261.97   $261.95   $262.00  
  Purchase #2 $103.36   10.292%   $113.9978   $114.00   $114.00   $114.00  
  Purchase #3 $43.41   13.136%   $49.1123   $49.11   $49.10   $49.10  
  Purchase #4 $90.74   3.477%   $93.895   $93.90   $93.90   $93.90  
  Purchase #5 $121.63   13.128%   $137.5976   $137.60   $137.60   $137.60  
  Purchase #6 $133.57   13.656%   $151.8103   $151.81   $151.80   $151.80  
  Purchase #7 $53.28   10.358%   $58.7987   $58.80   $58.80   $58.80  
  7 purchase totals = $793.55       $867.1846   $867.19   $867.15   $867.20