Magento Expert and Developer with Coding Experience

On my Magento built website in the order by pack quantity (product page) I need to prevent customers adding a decimal point like the example in the attached word document 1.2 pack quantity. If they order 1.2 packs the quantity should default to 1 and if they order 1.5 or above the pack quantity should default to 2. There are 2 locations on my website I need this function implementing. Customers should only be able to order in full quantity with no decimal points i.e. 1, 2, 5, 10, 15 packs and NOT 1.2, 3.4, 8.6, 10.8, 12.4 etc.. See examples in the attached file. Depending how this is implemented this should not conflict any other calculations on my website i.e. if the order 1 pack of 15.5m2 and want to order 4 extra m2 the area coverage should be 15.5 + 4 and the total area coverage you see in the box on the right should be 19.5m2. Any changes made to the website so not create any conflicts to how the website works today.