With all the assorted what does it cost to live ... posts, let me point you to the official numbers. The Nicaraguan government, through the Ministerio de Trabajo, offers what is called the Canasta Basica. It is a list of current costs for what MITRAB considers necessities. It is used to help set wage minimums but it is a good source of the typical costs of items from eggs to detergent.
This link is the latest as of this post but look around the site as it is updated monthly. I believe the totals are for a family of four but the chart includes quantities and price per unit (a pound of beef, a roll of toilet paper, a KWh of electricity and so on.
In looking at it, I noticed that it even includes rent at C$900/month. That works out to about $40. (You can currently use C$23 to US$1 for the conversion.) Clearly, some people will spend more on certain items (or add things such as an Internet connection) but it is a reasonable place to start. What is certainly supports is the fact that you can get by here on much less than most places in the world, particularly those that have Winters.