No, is not posible. Mikrotik not use squid for proxy cache. Redirect width Mikrotik in transparent mode for 1 Squid server, then, these Squid make Round Robin or weight with others Squid.
Best Regards
Paul

Normis, there exists the possibility of adding methods of balancing of connections in the NAT? Example: Round Robin, Auto-Weight, weight weighted, and other. This is very important for ISPs.
Best Regards
Paul.