I'm of the belief that $5 wouldn't make too much of a difference.

Considering your current rate of sales, there's a buffer afforded by the price increase that'll enable you to absorb conversions lost on account of it.

Which is to say 10 sales currently produces 149.50 (keeping it simple and not taking iBill deductions/affiliate payouts in to account for simple presentation's sake).

10 sales at 19.95 would produce 199.50 gross.

With the difference between the two being $50, you could lose 3 sales out of 10 (at the original 14.95) and still come out ahead.

Would a 5 dollar difference dissuade 3 out of every 10 potential conversions? I think it's less than likely.

What you're also doing, mind you, is increasing what a revshare sale would generate for your affiliate. Assuming your payout percentages are competitive, that slight difference could be a webmaster's deciding factor on whether or not they choose to promote you. So there's the added benefit of increasing your appeal to a greater abundance and variety of traffic sources.

I say, nothing gambled, nothing gained. Go for it.