There are so many things wrong with your code. I'll start with the throwDice method.
Why bother passing in a value as a parameter if you immediately throw it away and assign a new value to the count variable?
Why are you not using the parameter in your formula to calculate the dice total?
The formula will not give correct results. The Math.random class generates numbers from 0.0 to .999999. Plugging those values into your formula:
1 + (6 * 0.0) = 1
1 + ( 6 * 0.999999) = 6
Therefore your method can only return values in the range of 1 ( which is impossible for 2 or more dice) to 6. What happens when there are two or more dice? Where are the values of 7 and upwards?
Now back to the main method:
Why do you have the loop displaying the histogram inside the other loop? I would expect the program to display it once at the end.
Why is the histogram display loop iterating "total" number of times? If the total is 2 how is it supposed to display the histogram for all other values above 2?