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 $105.82   8.601%   $114.9216   $114.92   $114.90   $114.90  
  Purchase #2 $32.92   4.141%   $34.2832   $34.28   $34.30   $34.30  
  Purchase #3 $68.90   13.316%   $78.0747   $78.07   $78.05   $78.10  
  Purchase #4 $188.81   13.646%   $214.575   $214.58   $214.60   $214.60  
  Purchase #5 $133.51   13.710%   $151.8142   $151.81   $151.80   $151.80  
  Purchase #6 $220.97   8.219%   $239.1315   $239.13   $239.15   $239.10  
  Purchase #7 $172.76   12.127%   $193.7106   $193.71   $193.70   $193.70  
  7 purchase totals = $923.69       $1,026.5108   $1,026.50   $1,026.50   $1,026.50