The Pokemon Currency is based off of Japanese Yen, but other than that, it has no connection to any other type of real word currency.
For example, one Pokeball is 200 Pokedollars. If you imagine Pokedollars as Yen, it'll be $2 USD converted, which suddenly makes much more sense.
The Pokémon Dollar and its symbol were both created for the English translation of the games. In the original Japanese versions (except for Colosseum and XD), the currency used is yen and the symbol used is 円, the kanji for yen. As such, the Pokémon Dollar is based on yen.
Also, much like the yen, most items have prices that are multiples of 100 or 1000. For comparison, in the Generation VI games, a taxi ride starts at 円 710, which is precisely the same starting tariff as in Japan.
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