Based on some experiments I did a long while back I'd always reckoned the D1 gave me a +2 / -3 EV range.
My guess would be that the D100 has a somewhat narrower range. Specifically I've found there's a significant difference between how the two handle highlights: the D1 seems to go into burn-out more gradually than the D100 so there's a better chance of recovering detail in RAW mode. At the other end of the range the D100 produces far less noise - and what there is is random and film grain like rather than the distinctive banded noise of the (original) D1 - but its ability to capture detail doesn't seem to extend any further.
Incidentally I doubt you'll see a 5 stop range in camera produced JPEGs - you'll have to shoot in RAW mode to get that. You'll also likely find the results look a bit flat if you try to retain the full dynamic range when you process them since you're reducing the 12-bit range of the CCD to an 8-bit format such as JPEG.