$5 would be plenty. 
But don't go under that because you'd possibly encounter a small balance waiver. That's when the company waives billing, resulting in a balance of zero being reported to the bureaus.
All utilization fractions round up. As an example. 0.000001% would round up to 1%.
I rotate my cards monthly around each reporting date that does not allow for overlapping. In order for this to work to my fullest I have had to, in a couple cases, request changes in my billing date (thus changing the reporting date as well). I have a total limit of $60,000+ and never keep more than 2% on any AZEO card in a month (my CL per card are fairly uniform and nearly equal). My total utilization is always under 0.26% (the highest), which equates to about $150 per monthly cycle. The lowest I ever had was $19 which was under 0.03%. So based upon my personal experience, using your limit, you should not have any problem as long as you keep at least $36 on a card. I do agree with others that say $5 is fine (I just won’t try it because it is too close for me.)
I’ve never had an issue with the “small balance waiver” that HeavenOhio mentioned, but have heard about it from others. I have had “refund checks” sent when I over paid close accounts. By close accounts I mean a credit card account that has a pending charge very close to the billing date. This is caused by my lovely bride who accidentally uses the card after the “do not use” date my spreadsheet assigns each card every month. I cannot pay the pending charge via the credit card company’s online system because it is still pending; so, I go to my bank’s Bill Payer portal and pay the amount. Occasionally the Bill Payer funds will get to the CC account while the payment is still pending. In most cases, the CC company will just “over credit” my account for a few days; however, Capital One Quicksilver tends to send the money back via a check. This is a pain in the neck, and as of today has not cost me a scoring ding. It rarely happens (no never has it happened yet) to other CC companies and I have taken Cap One QS away from my beloved.
Y