When you say that the WW puts out 5.0 Volts...is that what is stamped on the WW or have you measured it with a digital Voltmeter?
Is the supply regulated or not? Is it AC or DC?
When you put a load on it, does it continue to put out exactly 5.0 Volts?
LED's are current devices, not voltage devices. A slight increase or decrease will not do any significant harm.