To find the percentage of tax, you can use the formula:
\[ \text{Tax Percentage} = \left(\frac{\text{Tax Amount}}{\text{Cost Before Tax}}\right) \times 100 \]
In this case, the tax amount is $0.27, and the cost before tax (the price of the sandwich) is $4.50.
Plugging in the values:
\[ \text{Tax Percentage} = \left(\frac{0.27}{4.50}\right) \times 100 \]
Calculating the fraction:
\[ \frac{0.27}{4.50} \approx 0.06 \]
Now multiply by 100 to get the percentage:
\[ 0.06 \times 100 \approx 6 \]
So, the percentage of tax is approximately 6%.