In rectangular box

$V = 4(2.5)(1.25)$
$V = 12.5 ~ \text{in.}^3$

Unit price

$U = 25 / 12.5$

$U = 2 ~ \text{cents/in.}^3$

In cylindrical can

$V = \frac{1}{4}\pi (2.5^2)(2.5)$
$V = 12.2718463 ~ \text{in.}^3$

Unit price

$U = 10 / 12.2718463$

$U = 0.815 ~ \text{cents/in.}^3$

The cylindrical can is more economical.