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	$141.59	5.210%	$148.9668	$148.97	$148.95	$149.00
Purchase #2	$10.86	10.133%	$11.9604	$11.96	$11.95	$12.00
Purchase #3	$100.43	8.149%	$108.614	$108.61	$108.60	$108.60
Purchase #4	$228.35	10.370%	$252.0299	$252.03	$252.05	$252.00
Purchase #5	$206.34	11.845%	$230.781	$230.78	$230.80	$230.80
Purchase #6	$104.49	6.681%	$111.471	$111.47	$111.45	$111.50
Purchase #7	$197.69	12.784%	$222.9627	$222.96	$222.95	$223.00
7 purchase totals =	$989.75		$1,086.7858	$1,086.78	$1,086.75	$1,086.90