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 $248.51   5.669%   $262.598   $262.60   $262.60   $262.60  
  Purchase #2 $129.59   5.446%   $136.6475   $136.65   $136.65   $136.60  
  Purchase #3 $5.82   11.139%   $6.4683   $6.47   $6.45   $6.50  
  Purchase #4 $33.31   5.826%   $35.2506   $35.25   $35.25   $35.30  
  Purchase #5 $114.43   10.411%   $126.3433   $126.34   $126.35   $126.30  
  Purchase #6 $41.85   12.420%   $47.0478   $47.05   $47.05   $47.00  
  Purchase #7 $247.53   8.629%   $268.8894   $268.89   $268.90   $268.90  
  7 purchase totals = $821.04       $883.2449   $883.25   $883.25   $883.20