There is no reason to use a torque wrench on a top-cap bolt. As for stems and other small M5 bolts, 5Nm is almost always safe. Only use more if there is a slippage problem.

Personally, I know what the necessary torques feels like by hand and never use a torque wrench for any M5 or M6 bolt. If you don't get a feel for this work by hand, how will you ever make an adjustment out on the road?

Use the small torque wrench to tighten some bolts to 5Nm, then see how tight that feels with a short handled hex wrench or 4-5-6 Y-style wrench.