Can I flush this into my holding tank?

Let’s keep this really simple.  With the exception of a little cleaning product and toilet paper follow this rule:

If you did not eat it, if you did not drink it, don’t flush it!

One extra caution, just because the label says it is flushable or septic safe only means it will go down the pipe.  It does not mean it is good for the holding tank.  If you did not eat it and you did not drink it and you still flush it, you are begging for a tank problem in the future, most likely at the worst possible time.