Cost basis on tax statments shown as N/A for two investment sales whose proceeds were 1 penny each.

I think they were partial shares that were sold (0.0011 and 0.004).  Because they are so small I think that triggered the label of N/A for a cost basis on my statements.  Turbotax however is asking for a cost basis.  Do I leave it blank (will that trigger an audit), or put 0.00?  Thanks!