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	$131.44	10.159%	$144.793	$144.79	$144.80	$144.80
Purchase #2	$64.42	12.181%	$72.267	$72.27	$72.25	$72.30
Purchase #3	$99.98	11.381%	$111.3587	$111.36	$111.35	$111.40
Purchase #4	$129.46	12.422%	$145.5415	$145.54	$145.55	$145.50
Purchase #5	$139.86	13.523%	$158.7733	$158.77	$158.75	$158.80
Purchase #6	$126.53	5.574%	$133.5828	$133.58	$133.60	$133.60
Purchase #7	$50.27	3.728%	$52.1441	$52.14	$52.15	$52.10
7 purchase totals =	$741.96		$818.4604	$818.45	$818.45	$818.50