To find the percentage of tax on the chicken sandwich, you can use the following formula:
\[ \text{Tax Percentage} = \left( \frac{\text{Tax Amount}}{\text{Cost of Item}} \right) \times 100 \]
In this case, the tax amount is $0.27 and the cost of the sandwich is $4.50.
Plugging in the values:
\[ \text{Tax Percentage} = \left( \frac{0.27}{4.50} \right) \times 100 \]
Calculating this:
\[ \text{Tax Percentage} = \left( 0.06 \right) \times 100 = 6% \]
So, the percentage of tax on the chicken sandwich is 6%.