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 $244.53   6.627%   $260.735   $260.74   $260.75   $260.70  
  Purchase #2 $93.83   12.654%   $105.7032   $105.70   $105.70   $105.70  
  Purchase #3 $86.71   12.674%   $97.6996   $97.70   $97.70   $97.70  
  Purchase #4 $241.77   8.333%   $261.9167   $261.92   $261.90   $261.90  
  Purchase #5 $107.76   7.427%   $115.7633   $115.76   $115.75   $115.80  
  Purchase #6 $195.38   12.679%   $220.1522   $220.15   $220.15   $220.20  
  Purchase #7 $118.30   12.115%   $132.632   $132.63   $132.65   $132.60  
  7 purchase totals = $1,088.28       $1,194.6020   $1,194.60   $1,194.60   $1,194.60