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	$173.85	6.683%	$185.4684	$185.47	$185.45	$185.50
Purchase #2	$85.29	4.517%	$89.1425	$89.14	$89.15	$89.10
Purchase #3	$237.32	7.693%	$255.577	$255.58	$255.60	$255.60
Purchase #4	$80.77	6.554%	$86.0637	$86.06	$86.05	$86.10
Purchase #5	$76.37	3.563%	$79.0911	$79.09	$79.10	$79.10
Purchase #6	$146.44	12.841%	$165.2444	$165.24	$165.25	$165.20
Purchase #7	$64.40	8.852%	$70.1007	$70.10	$70.10	$70.10
7 purchase totals =	$864.44		$930.6878	$930.68	$930.70	$930.70