When I got home last night, I checked my auto insurance renewal letter to confirm the new premium. As I expected, the premium specified on the letter was $0.01 lower than what was charged to my chequing account.
At first, I felt I had an iron-clad case: they had charged me more than they said they would, and I should not have to pay my NSF fee. However, it then occurred to me that if I had kept even a $5 cushion in my chequing account, I would have avoided the fee anyway.
This kind of minor variation in income/expenses should be the sort of thing that I can manage through regular cash flow. An unexpected $0.01 should not put my account into overdraft. Although I'm technically in the right here, even the slightest bit of contingency planning would have saved me this hassle.
I can't quite bring myself to take my insurer to task over a $0.01 overcharge. I suspect that this is a rounding error on their part, and I'll keep tabs on my future charges to see whether the premium reverts to the "lower" amount.
The NSF fee is simply the price I have to pay for not planning for the unexpected. From here on, I will not let the balance in my primary chequing account fall below $5.