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 $248.36   7.549%   $267.1087   $267.11   $267.10   $267.10  
  Purchase #2 $26.74   12.554%   $30.0969   $30.10   $30.10   $30.10  
  Purchase #3 $214.65   8.754%   $233.4405   $233.44   $233.45   $233.40  
  Purchase #4 $43.37   7.641%   $46.6839   $46.68   $46.70   $46.70  
  Purchase #5 $77.90   12.103%   $87.3282   $87.33   $87.35   $87.30  
  Purchase #6 $250.41   13.297%   $283.707   $283.71   $283.70   $283.70  
  Purchase #7 $91.49   7.149%   $98.0306   $98.03   $98.05   $98.00  
  7 purchase totals = $952.92       $1,046.3958   $1,046.40   $1,046.45   $1,046.30