shimano105 don't have bearings (as a unit, like in a washing machine) but have balls and two cones and two cups, those can be greased if you want, but it's not necessary so often, only when it squeaks.

Bearing units such as truvativ gxp, cannot pe greased or opened, but is very convenient to replace the bearings if it's needed to. Since they are standard bearings 61805 2RS that means 6(balls), 18(load index and external dimension standard), 05 (5*5mm=25mm internal diameter), 2RS(sealed with friction plastic covers at both ends. - but this is not the case, you don't have bearings.