set page on p:datatable

In your managed bean you can try this code:

public void setPageDataTable() {
    final DataTable d = (DataTable) FacesContext.getCurrentInstance().getViewRoot()
        .findComponent("form:templateTable");
    int first = 1;
    if (d.getRowCount() % ROWS_DATATABLE == 0) {
        first = (d.getRowCount() - ROWS_DATATABLE);
    }
    else 
    {
        first = (d.getRowCount()/ROWS_DATATABLE)*ROWS_DATATABLE;
    }
    d.setFirst(first);
}

Call this method when you add a new row

if the datatable widgetVar is dataTableWidget then use this:

<script type="text/javascript">
            $(document).ready(function () {
                dataTableWidget.paginator.setPage(0);
            });
 </script>

I would do it without any JavaScript. Primefaces's datatable has a first attribute, which is the index of the first data to display.

<p:dataTable first="#{calculatePageTable.first}"/>
...
<p:commandButton value="Add a row" action="#{calculatePageTable.addRow}"/>

And your backing bean:

public class CalculatePageTable {
    private int first = 1;

    public int getFirst(){
        return first;
    }

    public void addRow(){
        // 1. your stuff for adding the row 
        ...
        // 2. switch to the row
        first = getFirstRowOnLastPage(); 
    }

    private int getFirstRowOnLastPage(){
        ...
    }
}