Errata....

I wrote:
Income Tax: * * =round((A1 - A2*31.67 - 1533)*28% + 302.95, 2)

That assumes that your gross wage less exemption -- that is, A1 -
A2*31.67 -- is between $1533 and $3202. To play it safer, you could
write:

=if(A1 - A2*31.76 < 1533, NA(), round((A1 - A2*31.67 - 1533)*28% +
302.95, 2))

If you get the value #N/A, you might want to post back for further
assistance.

Of course, that still assumes that your gross wage (less exemption) is
less than $3202. But that was part of your original assumptions,
because you said your marginal rate is 28%.