First, you would need to create an equation for this problem. Let x represent the unknown tax.
[tex] \frac{x}{10.50} [/tex] = [tex] \frac{5}{100} [/tex]
Next, you would cross multiply.
100x = 52.5
Now, all you would have to do is isolate the x. To do this, you would divide both sides by 100.
x = $0.525
I hope this helps!