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 $62.40   11.802%   $69.7644   $69.76   $69.75   $69.80  
  Purchase #2 $146.59   5.311%   $154.3754   $154.38   $154.40   $154.40  
  Purchase #3 $200.63   6.370%   $213.4101   $213.41   $213.40   $213.40  
  Purchase #4 $210.34   8.801%   $228.852   $228.85   $228.85   $228.90  
  Purchase #5 $226.67   13.763%   $257.8666   $257.87   $257.85   $257.90  
  Purchase #6 $68.61   10.223%   $75.624   $75.62   $75.60   $75.60  
  Purchase #7 $156.70   5.537%   $165.3765   $165.38   $165.40   $165.40  
  7 purchase totals = $1,071.94       $1,165.2690   $1,165.27   $1,165.25   $1,165.40