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	$222.78	8.206%	$241.0613	$241.06	$241.05	$241.10
Purchase #2	$130.75	5.437%	$137.8589	$137.86	$137.85	$137.90
Purchase #3	$150.81	5.309%	$158.8165	$158.82	$158.80	$158.80
Purchase #4	$9.73	4.167%	$10.1354	$10.14	$10.15	$10.10
Purchase #5	$55.87	12.424%	$62.8113	$62.81	$62.80	$62.80
Purchase #6	$207.45	10.113%	$228.4294	$228.43	$228.45	$228.40
Purchase #7	$229.88	4.628%	$240.5188	$240.52	$240.50	$240.50
7 purchase totals =	$1,007.27		$1,079.6316	$1,079.64	$1,079.60	$1,079.60