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 $22.55   9.194%   $24.6232   $24.62   $24.60   $24.60  
  Purchase #2 $107.84   5.863%   $114.1627   $114.16   $114.15   $114.20  
  Purchase #3 $57.81   5.774%   $61.1479   $61.15   $61.15   $61.10  
  Purchase #4 $124.90   4.441%   $130.4468   $130.45   $130.45   $130.40  
  Purchase #5 $225.34   4.743%   $236.0279   $236.03   $236.05   $236.00  
  Purchase #6 $77.74   13.436%   $88.1851   $88.19   $88.20   $88.20  
  Purchase #7 $95.75   5.778%   $101.2824   $101.28   $101.30   $101.30  
  7 purchase totals = $711.93       $755.8760   $755.88   $755.90   $755.80