If you need to change the sale price on the device when creating a basket you should have the settings to modify the sale price active. That is at Main menu > Database > Sales / Invoices > Settings > Sales Orders > Modify Sale Price
Main Menu > Database
Sales / Invoices
Settings > Sales Orders
Modify Sale Price
Activate the tags you need when typing a quantity on the basket
When creating the basket, select the item before entering the quantity touch the price tag and select the option to change the price
On the web version you may go to Settings > Sales orders > Orders
Set Modify sale price to Yes
On the basket touch the Sale price box to select the option
Keep in mind that when the price is the option Other. The value will be just apply on that sale. It will not change the Prices on the item.