Usually the value isn't a big deal for "power rails" which expect to have additional capacitors connected elsewhere. However, sometimes microcontrollers expose

Usually the value isn't a big deal for "power rails" which expect to have additional capacitors connected elsewhere. However, sometimes microcontrollers expose decoupling pins for use with internal voltage converters and regulators (for example the core voltage on older STM32 parts), and those require very specific values that correspond with the tuning of feedback networks and power converter design within the IC