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 $103.90   10.284%   $114.5851   $114.59   $114.60   $114.60  
  Purchase #2 $26.32   5.387%   $27.7379   $27.74   $27.75   $27.70  
  Purchase #3 $15.59   12.823%   $17.5891   $17.59   $17.60   $17.60  
  Purchase #4 $182.32   12.772%   $205.6059   $205.61   $205.60   $205.60  
  Purchase #5 $103.56   8.737%   $112.608   $112.61   $112.60   $112.60  
  Purchase #6 $249.46   3.344%   $257.8019   $257.80   $257.80   $257.80  
  Purchase #7 $210.43   7.608%   $226.4395   $226.44   $226.45   $226.40  
  7 purchase totals = $891.58       $962.3674   $962.38   $962.40   $962.30