Sliders by the Box

A food truck sells sliders only in boxes of $4$ and boxes of $5$. Call an order size "fillable" if it can be hit exactly using any combination of those boxes (for example $9 = 4 + 5$ and $40 = 5 \cdot 8$ are fillable). How many of the order sizes $1, 2, \ldots, 1000$ are fillable?