IRS allows First In, First Out; Last In, First Out; and Highest In, First Out. Make sure you apply the same method to every sale transaction. HIFO let's you count the sale price against the highest paid cost, which minimizes your gains for any given transaction, but may affect whether the sale is taxed at the long-term or short-term rate.

Make sure to DYOR. I'm no professional, just sharing my experience. 

 Thanks so much for taking time to explain.