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 $243.33   7.667%   $261.9861   $261.99   $262.00   $262.00  
  Purchase #2 $124.63   10.241%   $137.3934   $137.39   $137.40   $137.40  
  Purchase #3 $80.70   8.278%   $87.3803   $87.38   $87.40   $87.40  
  Purchase #4 $176.81   11.155%   $196.5332   $196.53   $196.55   $196.50  
  Purchase #5 $179.99   8.130%   $194.6232   $194.62   $194.60   $194.60  
  Purchase #6 $77.57   7.528%   $83.4095   $83.41   $83.40   $83.40  
  Purchase #7 $155.72   3.212%   $160.7217   $160.72   $160.70   $160.70  
  7 purchase totals = $1,038.75       $1,122.0474   $1,122.04   $1,122.05   $1,122.00