That's really an incredibly detailed and narrow question, but you're in luck because I also use Apple Pages (part of iWorks, and boy is it due for an update) and find it's a great replacement for the far more expensive Microsoft Word, including its ability to have sophisticated tables that are really embedded spreadsheets.

One of the best examples is the Invoice template, which is actually how I do invoicing too, as it happens. That's why I knew I could help you out with your question, actually, because I recently billed a client for 1.5 hours of time and noticed the same annoying thing in the program.

It's the classic tradeoff between sophisticated and complicated, really, and as with much in modern Apple software, it's the "Inspector" window that holds the key to fixing the problem.

But let's start there, with the problem itself.

Here's what I saw:

See that "2" under the "Quantity" heading? It's not actually a two, that's just rounding up because Pages doesn't know that decimals are acceptable in this context.

If I click into the individual table cell, you'll see what happens:

Well, that's totally different, and as you say, it's darn confusing for the client to see, say, 2 * $100 = $150 because of this rounding error.

To fix this particular table data cell, click once on the cell to ensure it's selected, then click on the table button in the Inspector. As you can see, it's 7th from the left / 4th from the right, a little yellow grid:

Almost there, but this is where you can modify the formatting and presentation of the table itself. That's not what we want, we want the formatting of individual cells. To get there, click on "Format" on the tabs. Now the options change:

Before we just add a few decimal points for the number cell, let's have a quick peek at the different cell formatting options:

That's quite a few. Notice "Currency" is an option, too: that gives you two decimal points (and what I mean when i say that is "digits displayed after the decimal point in the number" so it'll add zeroes as needed to ensure the display is correct. If you've entered "47", it'll display in Currency as "47.00", as you'd hope).

We'll stick with Number, however, and simply use the tiny arrows to change the decimal setting from "0" to "2":

Now when I click out of the individual table data cell, it does exactly what I want to have happen, shows a fractional value:

So there's your answer. Very specific question, very specific answer. In general, though, just remember that the Inspector window is the key to everything within Pages, Keynote and Numbers, along with many other Mac OS X applications.