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	$224.32	4.621%	$234.6858	$234.69	$234.70	$234.70
Purchase #2	$179.29	11.764%	$200.3817	$200.38	$200.40	$200.40
Purchase #3	$139.43	10.553%	$154.144	$154.14	$154.15	$154.10
Purchase #4	$105.63	5.269%	$111.1956	$111.20	$111.20	$111.20
Purchase #5	$155.60	3.631%	$161.2498	$161.25	$161.25	$161.20
Purchase #6	$152.64	13.145%	$172.7045	$172.70	$172.70	$172.70
Purchase #7	$97.91	5.748%	$103.5379	$103.54	$103.55	$103.50
7 purchase totals =	$1,054.82		$1,137.8993	$1,137.90	$1,137.95	$1,137.80