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	$154.77	12.255%	$173.7371	$173.74	$173.75	$173.70
Purchase #2	$120.60	8.390%	$130.7183	$130.72	$130.70	$130.70
Purchase #3	$77.78	11.122%	$86.4307	$86.43	$86.45	$86.40
Purchase #4	$189.65	8.127%	$205.0629	$205.06	$205.05	$205.10
Purchase #5	$179.87	5.836%	$190.3672	$190.37	$190.35	$190.40
Purchase #6	$182.70	5.203%	$192.2059	$192.21	$192.20	$192.20
Purchase #7	$33.58	11.759%	$37.5287	$37.53	$37.55	$37.50
7 purchase totals =	$938.95		$1,016.0508	$1,016.06	$1,016.05	$1,016.00