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 $69.99   8.716%   $76.0903   $76.09   $76.10   $76.10  
  Purchase #2 $136.38   8.709%   $148.2573   $148.26   $148.25   $148.30  
  Purchase #3 $185.96   4.617%   $194.5458   $194.55   $194.55   $194.50  
  Purchase #4 $241.43   9.230%   $263.714   $263.71   $263.70   $263.70  
  Purchase #5 $247.79   7.631%   $266.6989   $266.70   $266.70   $266.70  
  Purchase #6 $222.70   8.239%   $241.0483   $241.05   $241.05   $241.00  
  Purchase #7 $142.97   7.554%   $153.77   $153.77   $153.75   $153.80  
  7 purchase totals = $1,247.22       $1,344.1246   $1,344.13   $1,344.10   $1,344.10