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 $12.60   10.752%   $13.9548   $13.95   $13.95   $14.00  
  Purchase #2 $227.99   4.797%   $238.9267   $238.93   $238.95   $238.90  
  Purchase #3 $109.75   4.561%   $114.7557   $114.76   $114.75   $114.80  
  Purchase #4 $250.57   13.521%   $284.4496   $284.45   $284.45   $284.40  
  Purchase #5 $227.51   5.424%   $239.8501   $239.85   $239.85   $239.90  
  Purchase #6 $221.56   13.460%   $251.382   $251.38   $251.40   $251.40  
  Purchase #7 $199.42   6.609%   $212.5997   $212.60   $212.60   $212.60  
  7 purchase totals = $1,249.40       $1,355.9186   $1,355.92   $1,355.95   $1,356.00