To calculate the sales tax, you can use the formula:
\[ \text{Sales Tax} = \text{Cost} \times \text{Tax Rate} \]
Bailey's cost is $21.25 and the tax rate is 9% (or 0.09 as a decimal).
\[ \text{Sales Tax} = 21.25 \times 0.09 \]
Now, perform the multiplication:
\[ \text{Sales Tax} = 21.25 \times 0.09 = 1.9125 \]
Rounding this to two decimal places, Bailey will owe approximately $1.91 in sales tax.
So, the correct response is:
$1.91