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	$136.54	10.698%	$151.147	$151.15	$151.15	$151.10
Purchase #2	$69.67	12.838%	$78.6142	$78.61	$78.60	$78.60
Purchase #3	$112.58	4.866%	$118.0581	$118.06	$118.05	$118.10
Purchase #4	$53.63	10.568%	$59.2976	$59.30	$59.30	$59.30
Purchase #5	$226.99	6.476%	$241.6899	$241.69	$241.70	$241.70
Purchase #6	$214.47	12.186%	$240.6053	$240.61	$240.60	$240.60
Purchase #7	$54.58	7.488%	$58.667	$58.67	$58.65	$58.70
7 purchase totals =	$868.46		$948.0791	$948.09	$948.05	$948.10