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	$176.70	13.368%	$200.3213	$200.32	$200.30	$200.30
Purchase #2	$154.38	3.523%	$159.8188	$159.82	$159.80	$159.80
Purchase #3	$116.29	8.463%	$126.1316	$126.13	$126.15	$126.10
Purchase #4	$92.54	7.786%	$99.7452	$99.75	$99.75	$99.70
Purchase #5	$94.41	9.571%	$103.446	$103.45	$103.45	$103.40
Purchase #6	$250.60	3.388%	$259.0903	$259.09	$259.10	$259.10
Purchase #7	$117.25	10.748%	$129.852	$129.85	$129.85	$129.90
7 purchase totals =	$1,002.17		$1,078.4052	$1,078.41	$1,078.40	$1,078.30