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 $180.27   8.498%   $195.5893   $195.59   $195.60   $195.60  
  Purchase #2 $115.94   5.563%   $122.3897   $122.39   $122.40   $122.40  
  Purchase #3 $44.25   5.336%   $46.6112   $46.61   $46.60   $46.60  
  Purchase #4 $233.50   5.215%   $245.677   $245.68   $245.70   $245.70  
  Purchase #5 $154.58   7.158%   $165.6448   $165.64   $165.65   $165.60  
  Purchase #6 $70.34   7.128%   $75.3538   $75.35   $75.35   $75.40  
  Purchase #7 $67.42   13.163%   $76.2945   $76.29   $76.30   $76.30  
  7 purchase totals = $866.30       $927.5603   $927.55   $927.60   $927.60