Optionals and unwrapping

I made a one of my one programs while following along in the course and I ran across unwrapping earlier. I had to use it in a situation where I was appending a dictionary. The unwrapping happens under fun additem in Class "Table". My question is, is this appropriate in this situation?? (I saw the other discussion topic but it didn't answer my question)

MY CODE

/Enter order - a list of items //Total that list of items //Add tax //Print out list of items and total

var menu: [String:Float] = ["Burger":5.0,"Fries":2.0,"Shake":4.0]
var taxRate: Float = 0.0972

class Table { //Declare Vars var tableArray: [Float] = []

//Functions
//Adding items to specific tables ticket 

func addItem(item: String) -> String {
    tableArray.append(menu[item]!)
    return item
}

//Print Ticket

func print() -> (printer: Float, taxs: Float) {
    var total: Float = 0
    for count in tableArray.startIndex..<tableArray.endIndex{
        total += tableArray[count]
    }
    total = total + (total * taxRate)
    return (total,taxRate)

}

}

class Store {

//Declare Vars
//************

//Functions
//*********

func appendMenu (item item: String, price: Float) -> String {
    menu.updateValue(price, forKey: item)
    return item
}

//Adjusting the Tax Rate

func adjustTax(taxrate: Float) {
    taxRate = taxrate
}

}

let store1 = Store() let table1 = Table() let oddCouple = Table() let theNextCouple = Table()

//TESTING ***************** //*************************

oddCouple.addItem("Burger")

table1.addItem("Burger") table1.addItem("Fries") table1.addItem("Shake")

theNextCouple.addItem("Burger") theNextCouple.addItem("Burger") theNextCouple.addItem("Burger")

theNextCouple.print()

store1.appendMenu(item: "Mush", price: 2.75) store1.appendMenu(item: "More", price: 7.0)