I've searched the forum but have had no luck...was there a fix developed for when Money is not rounded correctly?

I use the following to calculate a customer discount:

// Calculates the discount amount

Subroutine CalculateDiscount()
var vPosDiscAmt as Double
IF DISCOUNT_PERCENT > 0
THEN
	{
	vPosDiscAmt = BILLING_SUBTOTAL * (DISCOUNT_PERCENT/100)
	DISCOUNT_AMOUNT = 0 - vPosDiscAmt
	if @error then WriteLn("Error calculating discount amount")
	}
ELSE
IF (@ISBLANK(DISCOUNT_PERCENT) OR DISCOUNT_PERCENT = 0)
THEN
	{
	CLEAR(DISCOUNT_AMOUNT)
	}
End Subroutine 

This is in Global Code and is called when the DISCOUNT_PERCENT is changed.  I get some rounding errors.  For instance, if BILLING_SUBTOTAL is $1.50 and DISCOUNT_PERCENT is 5,  DISCOUNT_AMOUNT becomes $-0.07.  The actual value is -0.075, which I would like rounded up to -0.08.  If BILLING_SUBTOTAL is $1.57 and DISCOUNT_PERCENT is 10, DISCOUNT_AMOUNT becomes $-0.15.  The actual value is -0.157, which I would like rounded up to -0.16.  The only values I ever deal with for DISCOUNT_PERCENT are 5, 10 and 100.

Any pointers to some code that could fix this?  Is there a better way to calculate a percentage, perhaps a function I'm not aware of?  Thanks in advance.

Thanks Mark.  Based on this and some advice Ray gave me at the conference (using ToNumber to adjust my subtotal before performing math on it) I have come up with this:

// Calculates the discount amount

Subroutine CalculateDiscount()
var vPosDiscAmt as Double
var vDiscountUnrounded as Double
IF DISCOUNT_PERCENT > 0
THEN
	{
	vPosDiscAmt = (@ToNumber(BILLING_SUBTOTAL) * (DISCOUNT_PERCENT/100))
	vDiscountUnrounded = (0 - vPosDiscAmt)
	DISCOUNT_AMOUNT = (@Round(vDiscountUnrounded, 2))
	if @error then WriteLn("Error calculating discount amount")
	}
ELSE
IF (@ISBLANK(DISCOUNT_PERCENT) OR DISCOUNT_PERCENT = 0)
THEN
	{
	CLEAR(DISCOUNT_AMOUNT)
	}
End Subroutine 

This seems to be working, but it feels unwieldy, what with two variables getting into the mix.  Is there a more elegant way to do this?