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 $71.72   4.555%   $74.9868   $74.99   $75.00   $75.00  
  Purchase #2 $233.75   13.721%   $265.8228   $265.82   $265.80   $265.80  
  Purchase #3 $61.90   6.824%   $66.1241   $66.12   $66.10   $66.10  
  Purchase #4 $245.30   4.834%   $257.1578   $257.16   $257.15   $257.20  
  Purchase #5 $248.88   5.177%   $261.7645   $261.76   $261.75   $261.80  
  Purchase #6 $233.71   7.838%   $252.0282   $252.03   $252.05   $252.00  
  Purchase #7 $87.93   6.758%   $93.8723   $93.87   $93.85   $93.90  
  7 purchase totals = $1,183.19       $1,271.7565   $1,271.75   $1,271.70   $1,271.80