No, "banjo tuning" isn't an oxymoron, but it is a lifelong struggle. The nature of the banjo makes tuning it particularly difficult, since there's a tension between the strings and the drum-like head, not to mention the somewht flimsy (by musical instrument standards) construction, and changing any one item, like a string, affects all the other items (like the other strings). Change the tuning of one string, another has to be changed, which changes the first again (and all the others), which changes the one that had to be changed when you changed the first, which ....

Bob Clayton (author of "The Old-Timey Banjo Book," several copies of which are taking up room in my basement)