Typically I would have two accounts for this type of situation.  

One Tax free Roth for the client contributions , and one Tax Deferred with Before tax dollars for the company match. (The client should be able to report the balances of both components of the 401K.) The match and growth on the match will be treated as deferred and the Roth will be tax free.
 
In the event that the match, the contribution, and the growth are all supposed to be tax free, then I would use one TDBT account, selecting the checkbox for ITR (Independent Tax Rate).  Then add the column "Taxes- Ordinary Tax Rate" from the column field chooser and using that column set the taxation for this account to 0.