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 $69.27   8.470%   $75.1372   $75.14   $75.15   $75.10  
  Purchase #2 $186.73   5.834%   $197.6238   $197.62   $197.60   $197.60  
  Purchase #3 $77.38   7.726%   $83.3584   $83.36   $83.35   $83.40  
  Purchase #4 $86.74   12.271%   $97.3839   $97.38   $97.40   $97.40  
  Purchase #5 $159.34   4.445%   $166.4227   $166.42   $166.40   $166.40  
  Purchase #6 $248.57   5.290%   $261.7194   $261.72   $261.70   $261.70  
  Purchase #7 $126.33   5.141%   $132.8246   $132.82   $132.80   $132.80  
  7 purchase totals = $954.36       $1,014.4700   $1,014.46   $1,014.40   $1,014.40