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	$54.55	4.446%	$56.9753	$56.98	$57.00	$57.00
Purchase #2	$112.40	4.213%	$117.1354	$117.14	$117.15	$117.10
Purchase #3	$172.47	7.423%	$185.2724	$185.27	$185.25	$185.30
Purchase #4	$216.29	4.373%	$225.7484	$225.75	$225.75	$225.70
Purchase #5	$66.49	5.680%	$70.2666	$70.27	$70.25	$70.30
Purchase #6	$235.42	5.690%	$248.8154	$248.82	$248.80	$248.80
Purchase #7	$93.65	10.599%	$103.576	$103.58	$103.60	$103.60
7 purchase totals =	$951.27		$1,007.7895	$1,007.81	$1,007.80	$1,007.80