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	$96.57	3.150%	$99.612	$99.61	$99.60	$99.60
Purchase #2	$126.90	6.129%	$134.6777	$134.68	$134.70	$134.70
Purchase #3	$96.34	4.130%	$100.3188	$100.32	$100.30	$100.30
Purchase #4	$191.69	6.768%	$204.6636	$204.66	$204.65	$204.70
Purchase #5	$107.84	3.388%	$111.4936	$111.49	$111.50	$111.50
Purchase #6	$167.66	11.349%	$186.6877	$186.69	$186.70	$186.70
Purchase #7	$44.91	7.715%	$48.3748	$48.37	$48.35	$48.40
7 purchase totals =	$831.91		$885.8282	$885.82	$885.80	$885.90