Okay, I'm having a problem trying to figure out the way to spell and the meaning of all of the since/sinse/sence/since/cents(haha, know that one) but you get the point!
What is a good way for me to remember how to spell them at the right time and which one is appropriate?

Since: usually means because. "Puppy, since you don't sign into your IMs, I can't chat with you, privately, any longer."

Scents: aromas or odors. "Puppy, you really should stop wearing 11 different fragrances at once...the combination of that many scents drives us mere mortals to distraction."

Sense: to understand or feel. "Puppy, I sense you're not happy, evidenced by your frown, with my remarks about your tendency to wear 11 different fragrances at once."

While humorous (I hope), these should give you a good "sense" (understanding or feeling) of when to use which term.

Hope it helps.

Puppy, I see you're a pumpkin again (for now).

'Sinse' is not a word. 'Sence' is not a word on its own, only as part of words such as 'presence'.

'Since' can mean 'because', as Sonnet says. It has other meanings also, to do with time. 'Since I was a child', 'long since dead', 'it has since changed' are just some examples. A link didn't work, but look 'since' up in the Merriam-Webster link at the top of the page and you will see.

'Scents' can also be a verb. 'When my dog scents a fox ...', 'lavender scents the air' - always to do with smell.

'Sense' - a verb as Sonnet says, or a noun. As a noun, it can also have other meanings to do with intelligence. 'I hope you have more sense than to do that'. Again the M-W link will give you more detail.

How you remember which to use I have no idea, but since we have helped you to make sense of it I hope you will now follow up the scents we have given you, since it is a sense that scents the scents.

OK, I'll throw my 2 cents in to try to help with the spelling...
sINCE...I Need Certain Explainations..."since" I don't understand

sCENT...the new perfume was worth every CENT.

sENSE...Ever Need Someone Else...to explain something so that it makes "sense"

Do any of these memory techniques help out any?

Since you seem sincere miss blues,
I’m here to offer you some clues,
To begin we’ll start with cents
It takes many of them to pay our rents
And as for scents, just prefix an ‘s’
It could stand for smells, or so I guess
I hope this rhyme, to you, makes sense
Spelling’s a breeze; quit being so tense.

hmmm....well Kendor, that'll work if she doesn't have the same problem spelling "tense" as she did spelling "sense"

She's a wig wam, she's a teepee. She's a wigwam, she's a teepee..........

(She's two tents) [too tense?]

Thank you all for your replies. You all are very creative

I'm still struggling though. I don't know why it won't sink in, but I'll keep trying.
Thanks again for helping me.

At the Mall
Since I am out of cents, it doesn't make any sense to buy sensual scents.

or -

Because I have no money, it doesn't make any sense to purchase cologne.