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 $69.95   8.686%   $76.0259   $76.03   $76.05   $76.00  
  Purchase #2 $248.50   5.114%   $261.2083   $261.21   $261.20   $261.20  
  Purchase #3 $60.36   7.222%   $64.7192   $64.72   $64.70   $64.70  
  Purchase #4 $193.54   10.388%   $213.6449   $213.64   $213.65   $213.60  
  Purchase #5 $156.64   7.776%   $168.8203   $168.82   $168.80   $168.80  
  Purchase #6 $52.72   8.768%   $57.3425   $57.34   $57.35   $57.30  
  Purchase #7 $18.38   9.525%   $20.1307   $20.13   $20.15   $20.10  
  7 purchase totals = $800.09       $861.8918   $861.89   $861.90   $861.70