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	$177.51	12.869%	$200.3538	$200.35	$200.35	$200.40
Purchase #2	$118.47	12.133%	$132.844	$132.84	$132.85	$132.80
Purchase #3	$176.56	10.141%	$194.4649	$194.46	$194.45	$194.50
Purchase #4	$104.73	6.136%	$111.1562	$111.16	$111.15	$111.20
Purchase #5	$89.77	3.140%	$92.5888	$92.59	$92.60	$92.60
Purchase #6	$19.79	7.119%	$21.1989	$21.20	$21.20	$21.20
Purchase #7	$114.41	11.182%	$127.2033	$127.20	$127.20	$127.20
7 purchase totals =	$801.24		$879.8099	$879.80	$879.80	$879.90