Calculating the total of an order: Applying discounts
===

I'm working on an online orderform using javascript. I almost have it working, but what I would like to do is apply a 12.5% discount if more than 5 items are selected. So far I have managed to get the discount to apply if more than any one item is selected. Here is my code: 

    var totalItems = 0
    	
    // Run through the form fields to check for any filled fields
    for (var i=0; i<juiceForm.length; i++)
    {
    
    n=0;
    juicetotal = 0;
    itemQuantity = Number(parseInt(juiceForm[i].value)); // convert field value to a number
    		
    itemQuantity = parseInt(juiceForm[i].value);
    if (isNaN(itemQuantity)) 
    {
    itemQuantity = 0; // If the form field value is not a number, make it zero
    }
    
    // count the total number of juices selected
    totalItems = totalItems += Number(parseInt(juiceForm[i].value));
    
    if (totalItems >= 5 || itemQuantity >= 5 || (totalItems + itemQuantity) >= 5)
    {
    juiceTotal = (juiceTotal+(itemQuantity * juicePrice[i]))*0.875;
    }
    
    else 
    {
    
    // Multiply the quantity by the item price and update the order total	
    juiceTotal = juiceTotal+(itemQuantity * juicePrice[i]);
    }

Where I'm running into trouble is if multiple items are selected giving a total of more than 5 items, the calculation is coming out wrong. For example, if I have 5 crates of apple juice at £20 and 1 crate of orange at £22, with a 12.5% discount I should be getting a total of £106.75 but I am getting £95.81.

I'm not  sure if I have made an obvious mistake. Can anyone give me any advice on what I'm doing wrong?
