Lima is now $30.25 for intl flights. Only some AA tickets are exempt (because the tax was included in the fare). It's about $6.25 for domestic flights. There is a ATM right at the place where you pay the tax in case you don't have any cash.

Costa Rica has the same thing, forget how much it was (I went two years ago). You pay tax *before* check in which almost caused me to miss my flight because the lines were so long, I know they had a ATM there and took cash only, they accepted US$.