Figured it out using
/ip dhcp-server network
add address=192.168.88.0/24 dns-server=192.168.88.5 gateway=192.168.88.1 netmask=24
add address=192.168.88.5/32 dns-server=192.168.88.1 gateway=192.168.88.1 netmask=24
Solution by @vecernik87 http://forum.mikrotik.com/t/alternate-dns-for-specific-ip-on-lan-is-it-possible/125145/1
Now, how do I add a fallback script, something like this,with the above code:
:local currentDNS [/ip dns get server]
:local piholeDNS "192.168.88.5"
:local backupDNS "8.8.8.8,8.8.4.4"
:local testDomain "www.google.com"
:if ($currentDNS = $piholeDNS) do={
:do {
:resolve $testDomain server $piholeDNS
} on-error={
/ip dns set servers=$backupDNS
}
} else={
:do {
:resolve $testDomain server $piholeDNS
/ip dns set servers=$piholeDNS
} on-error={}
}