You have gotten some very good answers from 420,Melania,El primo and I am…ME.
So,I’ll just add a few.

Pase un buen dia.Have a good day.
Pase las buenas tardes.Have a good afternoon.
Pase las buenas noches.Have a good night.
De que talla busca?For which size are you looking?
Como quisiera pagar?How do you wish to pay?
Calzetines — Socks.
Zapatos — Shoes.
Pantalones — Pants.
Trajes — Suits
Trajes de bano(tilde over n).— Bathing suits.
Camisa — Shirt.
Estrecho or Aprietado(a) — Tight.
Cantidad — Quantity.
Cualidad — Quality.
Valor — Value.
Cuanto questa? — How much does it cost?
Cajero(a) — Cashier.
Ropa de hombre — Men’s clothing.
Ropa de Mujeres — Women’s clothing.
Cinta or Cinturon or Faja — Belt.
Baratillo — Sale(as in President’s Day Sale).
Venta — Sale.
Caro — Expensive.
Barato — Inexpensive.
Botas — Boots.
Corbata — Tie.
Chanclas — Dress shoes(Men’s).
Camison — Camisole or Nightgown.
Camiseta — Tee Shirt.
Chamarra — Jacket.
Pantaletas — Panties.
Ropa de Interior — Underwear.
Rebajo — Discount.
Reemplace — Replacement.
Cambio — Change(as in,Here is your change).
Cambiar — Exchange.
Medida — Measurement.
Pantalones de Mezclia — Blue Jeans.
Sombrero — Hat.
Cachucha — Cap(baseball cap).
Paragua — Umbrella.
Bolsa — Purse(also bag.as in,Desea una bolsa?Would you like a bag?)
Bolsillo — Wallet.
Como le puedo ayudar? — How may I help you? or Le puedo ayudar hallar algo? — Can I help you find something? or Como le puedo servir? — How may I serve you?
Que se le ofrece? — What would you like?
Que le puedo ofrecer hoy? — What can I offer you today?
Ancho(a) — Wide.
Angostito — Narrow(very narrow).
Espero que le guste nuesta tienda. — I hope you like our store.
Esperamos verla(o) de nuevo. — We hope to see you again. or
Esperamos que regrese. — We hope you’ll return.
Cuando se le ofresca algo,aqui estamos para servir. — Whenever you need something,we are here to be of service.
Cuando ya este’ listo(a)… — Whenever you’re ready…
A sus ordenes. — At your service.

Hope this all helps.

Are you finding everything ok today?- a podido encontrar todo lo necesario hoy? (grammatically speaking it is have you found all necessary things today?)
Is that all for today?- Es todo por hoy
is that all?- eso es todo? (asking when the person is giving the clothes to the cashier ready to pay)
Siza- Talla
S- Pequeño/Chico
XS- extra pequeño/Chico
M- mediano
L- grande
Over here please- por aqui porfavor
It is found over there/over here- Se encuentra por alla/por aqui
Have a nice day- Tenga un buen dia
Thanks for the buy (you don’t hear this very often in English, but you do in Spanish)- Gracias por su compra
Return another day- Vuelva otro dia
what are you looking for?- que es lo que anda buscando?
what size are you looking for?- Que talla anda buscando?
Hope that helps

For “Are you finding everything ok today?”
you can use:
Ha encontrado todo lo que buscaba?
or
Encontró lo que buscaba?
or just
Todo bien?

Size means “Talla”
small = pequeña
extra small = extra pequeña
medium = mediana
large = grande
extra large = extra grande

¿Cómo le puedo ayudar?=How can I help you?

¿Qué número calza?=What size shoe do you wear?

¿Cuál es su talla?=What size are you?

Le queda muy bien= It fits you very well

¿Cómo le queda?=How does it fit?

Estrecho/estrecha= tight(as in the shirt is too tight)

Ancho/ancha= loose

Pantalones=Pants

Camisa=Shirt

Traje=suit

Fajo=belt

Corbata=tie

Camisa a rayas= striped shirt

abrigo=coat

chamarra=jacket

de seda= made from silk:

de lana=made from wool.

Those are all i could think of for now.Hope it helps.

edit: ¿cómo quiere pagar?=How do you want to pay

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i do not understand bye… visit my question

como esta?- how r u
como le puedo alludar?- how can i help you
esta todo bien?- is everything alright
tiene algunas preguntas?- got any questions