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	$218.40	11.167%	$242.7887	$242.79	$242.80	$242.80
Purchase #2	$111.74	5.235%	$117.5896	$117.59	$117.60	$117.60
Purchase #3	$151.98	4.297%	$158.5106	$158.51	$158.50	$158.50
Purchase #4	$111.66	10.329%	$123.1934	$123.19	$123.20	$123.20
Purchase #5	$58.84	5.577%	$62.1215	$62.12	$62.10	$62.10
Purchase #6	$179.91	11.574%	$200.7328	$200.73	$200.75	$200.70
Purchase #7	$216.99	12.370%	$243.8317	$243.83	$243.85	$243.80
7 purchase totals =	$1,049.52		$1,148.7683	$1,148.76	$1,148.80	$1,148.70