When it comes to custom pricing and sales adjustments, you will not find a system with more flexibility.  Create custom sales and purchasing price levels supporting range values, give seasonal or periodic discounts for specific customers and/or a specific division within your company, for a specific period of time, for a select group of products or product categories.  See features below:

Sales and purchasing range levels:
Set up to 4 range levels with individual multiplier values.  Set filters for customer, division, product, product category or service item. These are multi select options.  Select one or more customers and or one or more divisions etc.

Option also available for showing adjustments separate at totals section of invoice or sales order.  Add any and/or many adjustments with custom label values.  Also supporting filters for customer, division, product, product category or service item (for invoicing).  Set your seasonal discounts and/or markups in the beginning and not have to worry about it again.

With filters it is very easy to target very specific pieces of data.  Dont be limited by the application when it comes to isolating data.