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 $60.76   3.637%   $62.9698   $62.97   $62.95   $63.00  
  Purchase #2 $93.87   12.773%   $105.86   $105.86   $105.85   $105.90  
  Purchase #3 $163.35   11.720%   $182.4946   $182.49   $182.50   $182.50  
  Purchase #4 $147.99   6.192%   $157.1535   $157.15   $157.15   $157.20  
  Purchase #5 $242.69   11.191%   $269.8494   $269.85   $269.85   $269.80  
  Purchase #6 $239.40   12.720%   $269.8517   $269.85   $269.85   $269.90  
  Purchase #7 $209.89   5.326%   $221.0687   $221.07   $221.05   $221.10  
  7 purchase totals = $1,157.95       $1,269.2477   $1,269.24   $1,269.20   $1,269.40