I put "declassified" in there because I saw a video a few years ago that claimed to show an A10 ripping through a tank. No idea what those rounds were.
Perhaps not through the front armor of a current MBT, but that's not where the guns aims. Instead it hits the top of the turret, the engine deck, and treads. This may not always result in an explosive, turret tossing engagement, but it definitely will result in a mission kill.
Every video I've ever seen of the A-10 involved it doing nasty things to tanks with its gun, at the very least rendering the tank inoperative. From wiki, sounds like it uses 5:1 mix of ~1 pound AP and HE rounds.
Like greedo alluded to, MBT armor is usually concentrated in the front (and angled) to defeat rounds from other tanks fired from roughly on the level, they tend to skimp everywhere else, and especially on the top.
I put "declassified" in there because I saw a video a few years ago that claimed to show an A10 ripping through a tank. No idea what those rounds were.