No, you don't need Server Gated Cryptology (SGC) to conduct secure transactions. SGC is a workaround to a now-repealed United States law that prevented US companies from exporting software using encryption higher than 40-bit. SGC allowed the encryption level to "step up" to 128-bit.
All modern browsers provide support for at least 128 bit encryption which, even with today's computers, cannot be compromised.
The only people affected by lower-bit encryption are using international versions of the following browsers and/or operating systems:
These antiquated browsers—Internet Explorer 3 was released in 1996 and Netscape no longer makes an Internet browser—are so old that the security risk from using them is greater than any risk posed by 40- bit encryption.
The reality is that SGC certificates offer no additional protection and can cost hundreds of additional dollars.