How to Calculate a %?

How to Calculate a %?

I have some data thats in a number, lets say 5455.
Id like to get the TAX from an input, say like 2.5 percent.

The formula is:
Tax Total = 5455 * .025 = 136.37
Actual Total = 5455 + 136.37 = Whatever.

$taxPercent = parseInt($('#tax').val());

This obviously isn't the right formula that's okay, I just don't know why I keep getting NaN. Im not sure if this will preserve the decimal either.

$('.bigTax').html($total * $taxPercent);