100 clicks will only give you a rough idea of conversion. To a 90% confidence (meaning the real answer is outside the range 1 in 10 times) here is what you get

none of which are particularly narrow ranges, I would suggest assuming the low end to start.)
Sales Test CR Confidence
error - + 1 1.00% 90%
1.970% -0.97% 2.97% 2 2.00% 90%
2.37% -0.37% 4.37% 3 3.00% 90%
2.69% 0.31% 5.69% 4 4.00% 90%
2.95% 1.05% 6.95% 5 5.00% 90%
3.18% 1.82% 8.18% 6 6.00% 90%
3.38% 2.62% 9.38% 7 7.00% 90%
3.57% 3.43% 10.57% 8 8.00% 90%
3.74% 4.26% 11.74% 9 9.00% 90%
3.89% 5.11% 12.89% 10 10.00% 90%
4.03% 5.97% 14.03%
Bah the table looks like shit...suffice it to say that 100 clicks will give you only a rough idea, the higher the conversion rate, the wider the margin of error.