At the Guasale to Choluteca, Honduras crossing:

Cost for visas: $12 per person ($2 tax and $10 for the tourist permit)
Cost for vehicle: $3 for fumigation. $12 for insurance. Permit is free.

There is an ATM in the immigration area on the Nicaraguan side that expenses cordobas and dollars.

Nicaragua is part of the CA-4 agreement. Most travellers are issued visas for 90-days that cover ALL CA-4 countries (Guatemala, El Salvador, Honduras and Nicaragua). If you spent 85 days in El Salvador and 2 days in Honduras then you have 3 days left to enjoy Nicaragua. Honduras does not enforce the 90 day policy as strictly as El Salvador and Nicaragua. 

 Here are photos and more details of for crossing this border with a vehicle.