Trying to find an efficient method to process all transactions directed to my BTC address

Question

I am building a website which involves in the processing of transactions of BTC. My current and most efficient plan to complete this would be to call these bitcoin-cli commands and process the data accordingly:
getblockcount - get block height
getblockhash blockheight-5 - get the block hash for the last 5 blocks
listsinceblock blockhash - list all transactions since then

I would run this order of commands every 5-10 seconds. I would like to know if this method wont screw me over at all (skipping transactions, etc). I might just be too paranoid about clients not getting what they paid for and just want a guaranteed method that no transactions slip by. I was hoping to call a method that can list all transactions since a certain time but that wasn't available. Now to the question:

Is this method CPU/Network intensive?
Is it a safe method?
What are my alternatives?

Answer 1

I have found the answer to my own question
To make sure every transaction goes through my script I have decided to use walletnotify. This is a feature of bitcoind and will run a bash script every time there is a new transaction with the transaction id. I was able to place this in my .bitcoin/bitcoin.conf file with the parameters like so:
walletnotify=/bin/echo %s | /bin/nc -U /root/nodejs.sock
I used netcat to bridge my requests from bash to NodeJS however you can use your %s transaction data any way you like.