tenin ga ryoukin to zeikin wo goukeisite kara, kurezittokaado de haraimasu.

Here, が marks 店員 as the subject of 合計して.

So the first part means that the clerk is the one who does the totaling.

は is also possible in some contexts, but it would sound more like you are setting up the clerk as the topic or contrasting them with someone else. In a clause like this, が is the more neutral and common choice.

Because 料金と税金 works as one combined object.

• 料金 = fee / charge
• 税金 = tax
• と = and

So 料金と税金を合計する means to total the charges and the tax.

Japanese often puts one particle after the whole list:

• りんごとバナナを食べる = eat apples and bananas
• 料金と税金を合計する = total the fee and tax

てから is a grammar pattern meaning after doing ...

So:

• 合計する = to total, add up
• 合計して = て-form of 合計する
• 合計してから = after totaling

This shows sequence:

1. the clerk totals the charge and tax
2. then the payment happens

So てから is about order of actions.

No. In this sentence, てから is a set pattern meaning after doing.

So:

• 払いますから... could mean because I will pay...
• 合計してから、払います means after totaling, pay

Even though the word から appears in both, the grammar is different here.

Not necessarily.

店員が clearly tells you that the clerk is the subject of the first action, 合計して. But the subject of 払います is omitted.

In Japanese, omitted subjects are very common. The second subject could be:

• I
• you
• the customer
• we

depending on the situation.

So this sentence can mean something like:

After the clerk totals the charges and tax, I / you / the customer pay(s) by credit card.

If you want to make it completely explicit, you could say:

店員が料金と税金を合計してから、私はクレジットカードで払います。

Here, で marks the means or method used to do something.

So:

• クレジットカードで払います = pay by credit card
• 現金で払います = pay in cash
• 箸で食べます = eat with chopsticks

Many learners first meet で as a location particle, but it also has this very common using / by means of function.

Because the object is understood from context.

Japanese often leaves out information that is obvious. Here, after talking about the total charge and tax, it is already clear that the person is paying the bill / the total amount.

So even though you could say something like:

• 料金を払います
• 代金を払います

it is very natural to omit the object when everyone knows what is being paid.

It is grammatical, but whether it sounds most natural depends on the situation.

Common related words:

• 料金 = fee / charge, often for services
• 代金 = the amount to be paid
• 値段 = price
• 合計金額 = total amount
• お会計 = the bill / check / checkout total

So this sentence is understandable, but in a real store or restaurant you might also hear wording closer to:

• 店員が合計金額を出してから、クレジットカードで払います。
• お会計のあと、クレジットカードで払います。

Also, 税金 is broad. If you specifically mean sales tax in Japan, 消費税 is often more precise.

Yes, it is correct and understandable.

That said, 合計する can sound a little formal or textbook-like depending on the context. In everyday speech, people may use expressions like:

• 計算する = calculate
• 合計を出す = work out the total
• お会計をする = do the checkout / bill

So 料金と税金を合計してから is fine, but it may sound a bit more explanatory than conversational.

Yes. Both can mean after totaling.

• 合計してから
• 合計したあとで

Both are natural, but てから often emphasizes the sequence a little more directly: first do A, then do B.

So in this sentence, 合計してから works very well because it highlights the order of events.

The comma simply marks a pause between the after clause and the main clause.

Japanese punctuation is often more flexible than English punctuation, so this comma is helpful but not absolutely required. The sentence could also be written without it.

Its job here is just to make the structure easier to read:

• first clause: 店員が料金と税金を合計してから
• main clause: クレジットカードで払います