In 1.92, you can do this without JavaScript.
You can create a hidden Equation question for each total you want to compute and store within the database. Say your question is "q1", your rows are named 1-4, and your sub-questions are named a-d. To compute the row total (let's call it q1_a_rowt), and round it to one decimal place, you would put this in the question field of that equation:
{round(sum(q1_a_1, q1_a_2, q1_a_3, q1_a_4),1)}
Then, assuming you did the same for rows b-d, the grand total would be:
{round(sum{q1_a_rowt, q1_b_rowt, q1_c_rowt, q1_d_rowt),1)}
Each of those equations values are automatically re-computed and stored in the database.