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	$155.59	11.247%	$173.0892	$173.09	$173.10	$173.10
Purchase #2	$43.85	13.765%	$49.886	$49.89	$49.90	$49.90
Purchase #3	$108.71	10.286%	$119.8919	$119.89	$119.90	$119.90
Purchase #4	$206.66	5.395%	$217.8093	$217.81	$217.80	$217.80
Purchase #5	$207.63	10.296%	$229.0076	$229.01	$229.00	$229.00
Purchase #6	$39.32	7.786%	$42.3815	$42.38	$42.40	$42.40
Purchase #7	$230.83	3.602%	$239.1445	$239.14	$239.15	$239.10
7 purchase totals =	$992.59		$1,071.2100	$1,071.21	$1,071.25	$1,071.20