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	$244.50	3.717%	$253.5881	$253.59	$253.60	$253.60
Purchase #2	$225.67	12.750%	$254.4429	$254.44	$254.45	$254.40
Purchase #3	$122.72	3.611%	$127.1514	$127.15	$127.15	$127.20
Purchase #4	$115.96	9.592%	$127.0829	$127.08	$127.10	$127.10
Purchase #5	$97.93	13.746%	$111.3915	$111.39	$111.40	$111.40
Purchase #6	$233.67	5.808%	$247.2416	$247.24	$247.25	$247.20
Purchase #7	$249.80	6.514%	$266.072	$266.07	$266.05	$266.10
7 purchase totals =	$1,290.25		$1,386.9704	$1,386.96	$1,387.00	$1,387.00