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	$106.95	4.185%	$111.4259	$111.43	$111.45	$111.40
Purchase #2	$179.30	3.537%	$185.6418	$185.64	$185.65	$185.60
Purchase #3	$82.58	7.126%	$88.4647	$88.46	$88.45	$88.50
Purchase #4	$43.60	10.242%	$48.0655	$48.07	$48.05	$48.10
Purchase #5	$111.49	10.766%	$123.493	$123.49	$123.50	$123.50
Purchase #6	$10.82	4.487%	$11.3055	$11.31	$11.30	$11.30
Purchase #7	$190.55	7.521%	$204.8813	$204.88	$204.90	$204.90
7 purchase totals =	$725.29		$773.2777	$773.28	$773.30	$773.30