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	$52.51	9.604%	$57.5531	$57.55	$57.55	$57.60
Purchase #2	$111.96	9.407%	$122.4921	$122.49	$122.50	$122.50
Purchase #3	$53.25	5.466%	$56.1606	$56.16	$56.15	$56.20
Purchase #4	$43.91	4.576%	$45.9193	$45.92	$45.90	$45.90
Purchase #5	$98.82	5.732%	$104.4844	$104.48	$104.50	$104.50
Purchase #6	$9.50	8.274%	$10.286	$10.29	$10.30	$10.30
Purchase #7	$207.94	4.113%	$216.4926	$216.49	$216.50	$216.50
7 purchase totals =	$577.89		$613.3881	$613.38	$613.40	$613.50