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	$228.76	5.565%	$241.4905	$241.49	$241.50	$241.50
Purchase #2	$214.58	7.429%	$230.5211	$230.52	$230.50	$230.50
Purchase #3	$239.53	11.164%	$266.2711	$266.27	$266.25	$266.30
Purchase #4	$89.29	3.770%	$92.6562	$92.66	$92.65	$92.70
Purchase #5	$35.39	5.463%	$37.3234	$37.32	$37.30	$37.30
Purchase #6	$120.76	10.784%	$133.7828	$133.78	$133.80	$133.80
Purchase #7	$183.30	7.430%	$196.9192	$196.92	$196.90	$196.90
7 purchase totals =	$1,111.61		$1,198.9643	$1,198.96	$1,198.90	$1,199.00