Great question! We cover this in the "Essentials" chapter of Moon Nicaragua -- here is an excerpt:
Bargaining
Looking for a good deal is a sport in Nicaragua--half social, half business, and is expected with most outdoor market vendors and taxi drivers. But be warned: Bargaining is al suave! Aggressive, prolonged haggling is not cool, won't affect the price, and may leave ill feelings. To start off the process, after you are given the initial price, act surprised and use one of the following phrases: "Que es lo menos?" (What is your lowest price?) or "Nada menos?" (Nothing less?).
Remember these guidelines when bargaining:
• Bargaining is social and friendly, or at least courteous. Keep your temper under wraps and always smile.
• Go back and forth a maximum of two or three times, and then either agree or walk away. Remember that some Nicaraguans, to save face, may lose a profit.
•When bargaining with taxi drivers in Managua, bargain hard, but agree on a price before you enter the cab--once the vehicle is moving, your leverage has vanished in a puff of acrid, black exhaust.
thanks for the info..