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 $107.53   6.236%   $114.2356   $114.24   $114.25   $114.20  
  Purchase #2 $246.51   6.103%   $261.5545   $261.55   $261.55   $261.60  
  Purchase #3 $10.80   10.211%   $11.9028   $11.90   $11.90   $11.90  
  Purchase #4 $177.71   7.867%   $191.6904   $191.69   $191.70   $191.70  
  Purchase #5 $226.88   6.738%   $242.1672   $242.17   $242.15   $242.20  
  Purchase #6 $184.30   9.468%   $201.7495   $201.75   $201.75   $201.70  
  Purchase #7 $73.86   6.231%   $78.4622   $78.46   $78.45   $78.50  
  7 purchase totals = $1,027.59       $1,101.7622   $1,101.76   $1,101.75   $1,101.80