If u r supplying 3.3V then voltage at Va output can never reach 5V. And since the Va is directly connected to Vcc, the tolerance of Va is equal to tolerance of Vcc.
Considering ideal conditions where the values are ideal, the Vcc = 3.3V and so Va=3.3V
then Vb=3.3*1000/(1000+1000) = 1.65V
Now, taking all the values to their lower side of tolerance, Vcc = Va = 3.3-0.01=3.29V, R1=R2=990 i.e. -1% tolerance
then Vb=3.29*990/(990+990) = 1.645V
Now, repeating for higher tolerence we get, Vcc = Va = 3.3+0.01=3.31V, R1=R2 = 1010 i.e. +1% tolerance
then Vb=3.31*1010/(1010+1010) = 1.655V
So, Vb is 1.65V +/- 5mV
Hope that helps.