According to their specs, https://d19y4lldx7po3t.cloudfront.net/assets/docs/coinspecs_022615v2.pdf :

1.5 MINING ALGORITHM
The exact hashing algorithm used is a combination of the 5 finalist algorithms that NIST selected as
candidates for SHA3 (BLAKE, Grøstl, JH, Keccak and Skein). The first in the series, Keccak, is executed,
and then the order of the next four is determined based on the result. In addition, there is an opt-in
process of mining with Proof of Knowledge of transaction data that allows miners to gain a 5% increase
in rewards. Read more about this here.