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	$32.52	9.852%	$35.7239	$35.72	$35.70	$35.70
Purchase #2	$244.90	9.127%	$267.252	$267.25	$267.25	$267.30
Purchase #3	$211.54	4.862%	$221.8251	$221.83	$221.85	$221.80
Purchase #4	$219.89	4.477%	$229.7345	$229.73	$229.75	$229.70
Purchase #5	$103.55	7.286%	$111.0947	$111.09	$111.10	$111.10
Purchase #6	$105.98	6.549%	$112.9206	$112.92	$112.90	$112.90
Purchase #7	$146.73	7.713%	$158.0473	$158.05	$158.05	$158.00
7 purchase totals =	$1,065.11		$1,136.5981	$1,136.59	$1,136.60	$1,136.50