A 12% general sales tax is levied on everything except goods bought at open-air markets and street vendors. It's usually included in the advertised or posted price and should be included with food and drink. If a business offers you a discount for paying in cash, it probably means they aren't charging sales tax (and not reporting the transaction to the government). Honduras has no tax-refund scheme for foreign visitors.
In addition to the sales tax, hotels are also required to charge a 4% tourism tax. Small mom-and-pop lodgings may forego this if you pay in cash.
Departure taxes at Honduras's four international airports—Tegucigalpa, San Pedro Sula, La Ceiba, and Roatán—are US$37.35 or L706 for international flights, and you'll pay L37.03 for domestic flights at any of the country's airports.