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 $119.83   4.714%   $125.4788   $125.48   $125.50   $125.50  
  Purchase #2 $35.32   6.540%   $37.6299   $37.63   $37.65   $37.60  
  Purchase #3 $98.31   12.803%   $110.8966   $110.90   $110.90   $110.90  
  Purchase #4 $60.33   3.534%   $62.4621   $62.46   $62.45   $62.50  
  Purchase #5 $164.96   5.628%   $174.2439   $174.24   $174.25   $174.20  
  Purchase #6 $247.99   5.773%   $262.3065   $262.31   $262.30   $262.30  
  Purchase #7 $21.45   7.532%   $23.0656   $23.07   $23.05   $23.10  
  7 purchase totals = $748.19       $796.0834   $796.09   $796.10   $796.10