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	$230.54	8.825%	$250.8852	$250.89	$250.90	$250.90
Purchase #2	$74.40	13.715%	$84.604	$84.60	$84.60	$84.60
Purchase #3	$226.28	3.231%	$233.5911	$233.59	$233.60	$233.60
Purchase #4	$187.45	12.580%	$211.0312	$211.03	$211.05	$211.00
Purchase #5	$111.41	6.687%	$118.86	$118.86	$118.85	$118.90
Purchase #6	$127.28	13.818%	$144.8676	$144.87	$144.85	$144.90
Purchase #7	$21.77	13.278%	$24.6606	$24.66	$24.65	$24.70
7 purchase totals =	$979.13		$1,068.4997	$1,068.50	$1,068.50	$1,068.60