It's a graduated income tax.
If you make a pittance on eBay, obey the law and declare it.
It probably won't make any difference to the amount of tax you pay.
https://www.canada.ca/en/revenue-agency/services/tax/individuals/frequently-asked-questions-individu...
You only pay 15% on your income under $57,375 or less, and most people don't pay any tax on the first $17K or so because of normal deductions.
If you don't give eBay your SIN, they will not transfer your customer payments to your checking account.
Based on your Sold listings so far, you are probably going to garner nearly $3000 this year.