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 $23.31   5.706%   $24.6401   $24.64   $24.65   $24.60  
  Purchase #2 $60.97   8.526%   $66.1683   $66.17   $66.15   $66.20  
  Purchase #3 $152.93   13.162%   $173.0586   $173.06   $173.05   $173.10  
  Purchase #4 $63.89   10.244%   $70.4349   $70.43   $70.45   $70.40  
  Purchase #5 $209.61   5.193%   $220.495   $220.50   $220.50   $220.50  
  Purchase #6 $107.28   8.534%   $116.4353   $116.44   $116.45   $116.40  
  Purchase #7 $110.76   3.655%   $114.8083   $114.81   $114.80   $114.80  
  7 purchase totals = $728.75       $786.0405   $786.05   $786.05   $786.00