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	$148.60	6.804%	$158.7107	$158.71	$158.70	$158.70
Purchase #2	$12.56	6.808%	$13.4151	$13.42	$13.40	$13.40
Purchase #3	$160.58	3.634%	$166.4155	$166.42	$166.40	$166.40
Purchase #4	$143.92	7.430%	$154.6133	$154.61	$154.60	$154.60
Purchase #5	$102.34	8.523%	$111.0624	$111.06	$111.05	$111.10
Purchase #6	$39.85	9.387%	$43.5907	$43.59	$43.60	$43.60
Purchase #7	$239.88	8.158%	$259.4494	$259.45	$259.45	$259.40
7 purchase totals =	$847.73		$907.2571	$907.26	$907.20	$907.20