It's not optimal, but I doubt it would truly harm and otherwise healthy dog. Just be sure he stays well hydrated and use really good sanitary precautions...handwashing, picking up stools immediately and disposing properly, don't let the dog sleep on your bed or furniture, be prepared once he is wormed to wash all bedding in hot water...
roundworm info...
http://www.marvistavet.com/html/body...__puppies.html
I noticed that fenbendazole works for roundworms...known as Panacur from the vet, or Safeguard over the counter. If there is a feed store nearby I would consider calling to ask if they carry the small bottle of liquid goat Safeguard wormer. Following is a website that will help you determine the proper dosing for a dog. The wormer should run about $15 and you can keep it refrigerated for up to 3 years, especially good if you live in a warm climate prone to parasites. Be sure to scroll down to the yellow highlighted text.
http://www.beaglesunlimited.com/beag...tinalworms.htm