Most Dominicans(incl the gov't) will tell you to not throw the toilet paper in the toilet. The reasons are due to a number of reasons. One, the poor condition of the sanitary sewer system, two, to make things simple for the people, ie they might be confused as to what type of paper can be used and if the system is onsite or public - onsite systems clog up faster with paper of any kind because of the lack of a septic tank to separate the solids fom the effluent. Three, even though they have all of the plumbing equipment for large and small sewers here, they don't have the resources to be constantly using them.
As a civil engineer I am well familiar with sanitary sewer design, etc. and I personally throw the paper down the toilet wherever I go and have never have had a problem. Therefore, even though the sanitary systems here are suspect, given the low number of foreigners I say toss it down the toilet as long as it is a public system. If it is an onsite system, depending on the state of the sewage pit, it may or may not affect it. The sandier soil one has on their property, the better though.