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 $67.58   5.356%   $71.1996   $71.20   $71.20   $71.20  
  Purchase #2 $147.83   3.697%   $153.2953   $153.30   $153.30   $153.30  
  Purchase #3 $226.69   5.451%   $239.0469   $239.05   $239.05   $239.00  
  Purchase #4 $175.55   4.167%   $182.8652   $182.87   $182.85   $182.90  
  Purchase #5 $105.57   10.291%   $116.4342   $116.43   $116.45   $116.40  
  Purchase #6 $221.70   7.615%   $238.5825   $238.58   $238.60   $238.60  
  Purchase #7 $188.77   13.670%   $214.5749   $214.57   $214.55   $214.60  
  7 purchase totals = $1,133.69       $1,215.9986   $1,216.00   $1,216.00   $1,216.00