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	$106.67	4.382%	$111.3443	$111.34	$111.35	$111.30
Purchase #2	$228.71	6.283%	$243.0798	$243.08	$243.10	$243.10
Purchase #3	$111.42	7.274%	$119.5247	$119.52	$119.50	$119.50
Purchase #4	$5.99	13.324%	$6.7881	$6.79	$6.80	$6.80
Purchase #5	$37.30	11.402%	$41.5529	$41.55	$41.55	$41.60
Purchase #6	$90.60	13.766%	$103.072	$103.07	$103.05	$103.10
Purchase #7	$174.25	3.366%	$180.1153	$180.12	$180.10	$180.10
7 purchase totals =	$754.94		$805.4771	$805.47	$805.45	$805.50