what you could do is to average 4, 8 or 16 readings (powers of 2 gives best performance)
void loop()
{
float raw = 0;
for (int i=0; i< 16; i++) raw = raw + analogRead(tempPin);
raw = raw / 16;
float milivolts = (raw /1024.0) * 500;
float temp = milivolts * 100;
give it a try