I built my own power conditioner box which is acting currently as just a power strip. I used 12awg wire, not 10 and this was difficult enough. I like Mike's suggestion for crimping, and I might add solder for good measure too. However, I give you some ideas I've tried and thing I've learned as well.
I used a barrier strip for connecting all the hots together, neutrals together. Some might not like this idea but it worked. If the crimping doesn't work, this might. The larger ones have screw terminals and you can wrap the copper wire around the terminals. Bring each wire to its own terminal but also use a piece of stripped wire that strings together each terminal that you wish to join. So this wire wraps around the first terminal then onto the second, wrapping around it and then onto the next, etc. This way each terminal only has to hold two wire thicknesses, not 5-6, and the current doesn't have to conduct through the barrier strip, it is going from bare wire to bare wire. Its also tidy and makes maintainence or changes easy.
For the ground I use a relatively long bronze bolt through the case and eyelet crimp terminals. I crimped the ends of each ground wire with an eyelet and then bolted them to the case in a star configuration.
However, I have since found something available at home depot which I think would work even better. They sell earth ground connectors that are solid copper. They are a thick block with a hole for bolting to the case (or the ground source) and then have a hole in the block with a screw down bolt. You place the bare wire into the hole and screw down tight. They sell these in various sizes. I am pretty sure you could find one that could accept all 5 10awg. I'd twist the ends together with a pair of plier and then put in the hole and screw down tight. It might work for hot and neutral too if you heatshrink it after or insulate it. These were in the electrical department.
