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	$145.96	13.585%	$165.7887	$165.79	$165.80	$165.80
Purchase #2	$102.25	11.180%	$113.6816	$113.68	$113.70	$113.70
Purchase #3	$153.72	5.575%	$162.2899	$162.29	$162.30	$162.30
Purchase #4	$105.62	11.872%	$118.1592	$118.16	$118.15	$118.20
Purchase #5	$115.98	6.680%	$123.7275	$123.73	$123.75	$123.70
Purchase #6	$209.62	11.202%	$233.1016	$233.10	$233.10	$233.10
Purchase #7	$45.37	11.493%	$50.5844	$50.58	$50.60	$50.60
7 purchase totals =	$878.52		$967.3329	$967.33	$967.40	$967.40