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	$100.57	4.469%	$105.0645	$105.06	$105.05	$105.10
Purchase #2	$178.34	7.619%	$191.9277	$191.93	$191.95	$191.90
Purchase #3	$93.81	7.246%	$100.6075	$100.61	$100.60	$100.60
Purchase #4	$216.76	6.280%	$230.3725	$230.37	$230.35	$230.40
Purchase #5	$111.91	5.514%	$118.0807	$118.08	$118.10	$118.10
Purchase #6	$62.74	11.745%	$70.1088	$70.11	$70.10	$70.10
Purchase #7	$137.45	7.696%	$148.0282	$148.03	$148.05	$148.00
7 purchase totals =	$901.58		$964.1899	$964.19	$964.20	$964.20