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	$184.59	3.617%	$191.2666	$191.27	$191.25	$191.30
Purchase #2	$183.49	11.809%	$205.1583	$205.16	$205.15	$205.20
Purchase #3	$95.38	5.278%	$100.4142	$100.41	$100.40	$100.40
Purchase #4	$46.68	11.698%	$52.1406	$52.14	$52.15	$52.10
Purchase #5	$159.35	12.753%	$179.6719	$179.67	$179.65	$179.70
Purchase #6	$48.42	7.396%	$52.0011	$52.00	$52.00	$52.00
Purchase #7	$111.80	4.190%	$116.4844	$116.48	$116.50	$116.50
7 purchase totals =	$829.71		$897.1371	$897.13	$897.10	$897.20