5 gallons is the minimal size container recommended for growing tomatoes.

Koralik is listed as both a determinate and an indeterminate but neither would survive in that small a pot. Never grown it so can't say how big it will get but it would quickly get rootbound.

Golden Nugget is a more compact plant but still easily reach 2 1/2 feet tall.

Dave

More important than the pot, perhaps, is how large the vine will grow and whether you have room for it indoors -- and how you'll support it if you do have room.

For varieties which do not grow so tall, see the "Container Tomatoes" and "Dwarf Tomatoes" sections in Tatiana's TOMATObase:
http://t.tatianastomatobase.com:88/wiki/Category:Container_Tomatoes
http://t.tatianastomatobase.com:88/wiki/Category:Dwarf_Tomatoes

In some cases the articles cite plant height.

Some people do say it's possible to grow some smaller-vined tomatoes in containers under 5 gallons -- but details are difficult to come by.

===

If you're ever contemplating using a container you don't know the size of, you can calculate the volume in inches, then divide the total by 231. That will give you the number of gallons.