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 $213.99   11.569%   $238.7465   $238.75   $238.75   $238.70  
  Purchase #2 $44.66   6.797%   $47.6955   $47.70   $47.70   $47.70  
  Purchase #3 $114.76   13.455%   $130.201   $130.20   $130.20   $130.20  
  Purchase #4 $172.51   10.487%   $190.6011   $190.60   $190.60   $190.60  
  Purchase #5 $233.77   6.192%   $248.245   $248.25   $248.25   $248.20  
  Purchase #6 $94.97   10.119%   $104.58   $104.58   $104.60   $104.60  
  Purchase #7 $24.56   7.231%   $26.3359   $26.34   $26.35   $26.30  
  7 purchase totals = $899.22       $986.4050   $986.42   $986.45   $986.30