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 $140.98   7.804%   $151.9821   $151.98   $152.00   $152.00  
  Purchase #2 $240.66   8.693%   $261.5806   $261.58   $261.60   $261.60  
  Purchase #3 $48.70   11.271%   $54.189   $54.19   $54.20   $54.20  
  Purchase #4 $74.27   5.216%   $78.1439   $78.14   $78.15   $78.10  
  Purchase #5 $112.92   12.512%   $127.0486   $127.05   $127.05   $127.00  
  Purchase #6 $44.65   8.848%   $48.6006   $48.60   $48.60   $48.60  
  Purchase #7 $115.41   4.109%   $120.1522   $120.15   $120.15   $120.20  
  7 purchase totals = $777.59       $841.6970   $841.69   $841.75   $841.70