Hopefully this coupon plays nice with others, with $10 off 75 you could do:
4x photo paper + 2x copy paper + $1.06 filler - 15% paper - 10 off 75 = $8.05 MM - tax = ~$3 - $5 MM
So I went and tried the above transaction a couple hours ago. In this order, I applied: 10 off 75, then 10 off 50 office supplies, which stacked as expected. Then tried to add 15%. Register wouldn't take it.
Re-did the transaction, 15% first, then $10 off 75, then $10 off 50 office supplies. Register took this combo, but did *not* apply the $10 off 50 to any of the paper, only to a filler pack of $1 envelopes in the transaction. I knew something wasn't adding up right, but couldn't ask the cashier to void out yet another transaction. Big waste of a $10 off 50 as it only took $1 off the total.
Tried throwing a 20% off a single item and a $5 off 25 in the mix after all this, neither one was accepted by the register. Bottom line, it seems you can apply the 15% off and a single $-off coupon to the paper, no more.