how did you get the base current to be a little less than 5ma?
The output of the micro will be a bit less than 5 volts and the Vbe drop of the transistor is about .7 volts so 4.3/1000 = 4.3 ma.
the gain is abbreviated as hfe correct? reading the datasheet under the hfe section, did you take the ratio of Ic and the min value to get the value of 10?
hfe is specifies with 1 volt from collector to emitter, so you might only have 4 volts for your relay. Saturation is usually when base current is 1/10 of collector current and then the Vce drop is about .3 volts. (Page 2 of the datasheet)
I still don't see how that 10k resistor will make sure its off.
The transistor will start to turn on when the voltage on the base is .6 or .7 volts. The output from the micro in the low state is probably around .2 volts so the 10k probably serves no purpose. But should the micro be disconnected the base will be what I call floating. In this case a small bit of noise could turn on the transistor. The resistor to ground helps prevent this.