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 $114.44   3.532%   $118.482   $118.48   $118.50   $118.50  
  Purchase #2 $85.97   9.735%   $94.3392   $94.34   $94.35   $94.30  
  Purchase #3 $41.88   10.733%   $46.375   $46.38   $46.40   $46.40  
  Purchase #4 $151.29   3.730%   $156.9331   $156.93   $156.95   $156.90  
  Purchase #5 $148.62   13.515%   $168.706   $168.71   $168.70   $168.70  
  Purchase #6 $218.25   8.110%   $235.9501   $235.95   $235.95   $236.00  
  Purchase #7 $152.53   7.251%   $163.59   $163.59   $163.60   $163.60  
  7 purchase totals = $912.98       $984.3754   $984.38   $984.45   $984.40