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 $235.26   4.823%   $246.6066   $246.61   $246.60   $246.60  
  Purchase #2 $246.75   3.502%   $255.3912   $255.39   $255.40   $255.40  
  Purchase #3 $124.88   10.264%   $137.6977   $137.70   $137.70   $137.70  
  Purchase #4 $246.27   8.726%   $267.7595   $267.76   $267.75   $267.80  
  Purchase #5 $193.62   6.616%   $206.4299   $206.43   $206.45   $206.40  
  Purchase #6 $185.48   7.725%   $199.8083   $199.81   $199.80   $199.80  
  Purchase #7 $224.59   3.845%   $233.2255   $233.23   $233.25   $233.20  
  7 purchase totals = $1,456.85       $1,546.9187   $1,546.93   $1,546.95   $1,546.90