Adding a zero after computation

[stephanief]

Hi Everyone I've come across a little problem
I've been working on a simple shopping cart
and so far so good but after computing the
totals they do not appear as floats with 2 decimal
places (£2.50 is £2.5)..how can i avoid this problem.
Please help

Here's my code:

$total2=$light_packages * $price2 * $years_light;