So, it looks like Test 6 checks stuff like

BID 0.0149

Am I right?
If yes, what the hell should we use?
I used both:

cur=floorl(cur1*100.0+0.5);

and

cur=cur1*100;

WA6 both times. What the hell?

I think that your problem is not in kind of round. The first way should be ok.

I have WA6 too with some error. Try test:

BID 100
BID 101
BID 100.01
SALE 100.01 3
QUIT

My program doesn't work good in it.

-