It's not about sales tax, it's about income tax. Depending on your income and the way your business is set up - you'll most likely need to file quarterly. More income more frequent filing.
You would do well to contact your accountant or at least a bookkeeping service and outsource this.
If you are a part time business you can have your current employer increase your FICA withholdings.
It really depends on what you make. But the IRS tends to like people to file by the rules regardless of income.
Not something to play around with. And FICA can easily come back and bite you as you are required to pay the full 15.3% (perhaps a fraction higher now - I don't know because I outsource all the paperwork) up to about 89K in income.
The rules are constantly changing and unfortunately pleading ignorance can get you severly penalized.
