Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$78.93	10.205%	$86.9848	$86.98	$87.00	$87.00
Purchase #2	$137.61	9.333%	$150.4531	$150.45	$150.45	$150.50
Purchase #3	$107.99	10.577%	$119.4121	$119.41	$119.40	$119.40
Purchase #4	$94.76	4.710%	$99.2232	$99.22	$99.20	$99.20
Purchase #5	$40.54	9.531%	$44.4039	$44.40	$44.40	$44.40
Purchase #6	$119.25	3.414%	$123.3212	$123.32	$123.30	$123.30
Purchase #7	$106.75	4.200%	$111.2335	$111.23	$111.25	$111.20
7 purchase totals =	$685.83		$735.0318	$735.01	$735.00	$735.00