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 $194.63   9.566%   $213.2483   $213.25   $213.25   $213.20  
  Purchase #2 $157.43   6.553%   $167.7464   $167.75   $167.75   $167.70  
  Purchase #3 $248.85   5.581%   $262.7383   $262.74   $262.75   $262.70  
  Purchase #4 $44.55   10.759%   $49.3431   $49.34   $49.35   $49.30  
  Purchase #5 $72.62   5.122%   $76.3396   $76.34   $76.35   $76.30  
  Purchase #6 $51.86   6.458%   $55.2091   $55.21   $55.20   $55.20  
  Purchase #7 $55.74   7.706%   $60.0353   $60.04   $60.05   $60.00  
  7 purchase totals = $825.68       $884.6601   $884.67   $884.70   $884.40