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   3.493%   $69.9406   $69.94   $69.95   $69.90  
  Purchase #2 $122.81   13.615%   $139.5306   $139.53   $139.55   $139.50  
  Purchase #3 $83.69   10.501%   $92.4783   $92.48   $92.50   $92.50  
  Purchase #4 $151.30   10.378%   $167.0019   $167.00   $167.00   $167.00  
  Purchase #5 $22.35   7.110%   $23.9391   $23.94   $23.95   $23.90  
  Purchase #6 $30.74   13.559%   $34.908   $34.91   $34.90   $34.90  
  Purchase #7 $200.58   11.864%   $224.3768   $224.38   $224.40   $224.40  
  7 purchase totals = $679.05       $752.1753   $752.18   $752.25   $752.10