Ripple charges

Ripple itself usually charges only a fraction of one XRP (typically ~1/10000th).

There are 2 other sources of "charges" that can happen:
1) Gateways can set transfer fees for their IOUs, meaning if this fee is e.g. 1%, you'd need to send 101 USD to have the recipient receive 100 USD. These fees can be set from 0% to 400%, so maybe check out the policy of the gateway first.

2) Markets can be illiquid (think of the situation when BTC were much more expensive on MtGox than elsewhere because they were the only thing left one could transfer out) meaning you might pay a premium to actually get the money you need to fulfill your payment - this is not a "fee" per se but in the end it might also mean that you might need to send more USD than what arrives at the recipient. Ripple at least offers the option that it searches for "paths" instead of just looking at a single order book - for example it might yield more USD if you first sell BTC for LTC and then LTC for USD instead of directly paying in BTC.

In practice currently it seems that many gateways set fees in 1) to about 0.2% per transaction, depending on which gateway you use the "fees" of 2) can vary a lot though - just like with the price quotes that BitPay or Coinbase give you...