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 $114.47   3.252%   $118.1926   $118.19   $118.20   $118.20  
  Purchase #2 $154.99   4.250%   $161.5771   $161.58   $161.60   $161.60  
  Purchase #3 $248.76   13.389%   $282.0665   $282.07   $282.05   $282.10  
  Purchase #4 $64.36   5.195%   $67.7035   $67.70   $67.70   $67.70  
  Purchase #5 $216.94   10.194%   $239.0549   $239.05   $239.05   $239.10  
  Purchase #6 $73.98   6.754%   $78.9766   $78.98   $79.00   $79.00  
  Purchase #7 $111.44   8.827%   $121.2768   $121.28   $121.30   $121.30  
  7 purchase totals = $984.94       $1,068.8480   $1,068.85   $1,068.90   $1,069.00