30 LEDS per meter - 5 meters = 150 LEDs.
If you only light up one channel at a time, that's 150 * 20mA = 3A
However, if you plan on lighting any combination of channels, you're going to need more. 150 LEDS x 3 channels (RGB) x 20mA (per channel) = up to 9A
You're going to run out of juice on that power supply if you turn the whole string on full white ... it will look more like a dark yellow to dark pink.