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 $23.60   10.418%   $26.0586   $26.06   $26.05   $26.10  
  Purchase #2 $224.73   4.167%   $234.0945   $234.09   $234.10   $234.10  
  Purchase #3 $69.86   3.341%   $72.194   $72.19   $72.20   $72.20  
  Purchase #4 $119.76   7.257%   $128.451   $128.45   $128.45   $128.50  
  Purchase #5 $42.60   12.775%   $48.0422   $48.04   $48.05   $48.00  
  Purchase #6 $151.48   4.436%   $158.1997   $158.20   $158.20   $158.20  
  Purchase #7 $50.36   12.476%   $56.6429   $56.64   $56.65   $56.60  
  7 purchase totals = $682.39       $723.6829   $723.67   $723.70   $723.70