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	$65.65	12.559%	$73.895	$73.90	$73.90	$73.90
Purchase #2	$41.77	4.433%	$43.6217	$43.62	$43.60	$43.60
Purchase #3	$91.50	6.491%	$97.4393	$97.44	$97.45	$97.40
Purchase #4	$99.40	13.178%	$112.4989	$112.50	$112.50	$112.50
Purchase #5	$148.57	4.577%	$155.37	$155.37	$155.35	$155.40
Purchase #6	$41.81	4.624%	$43.7433	$43.74	$43.75	$43.70
Purchase #7	$59.45	5.769%	$62.8797	$62.88	$62.90	$62.90
7 purchase totals =	$548.15		$589.4479	$589.45	$589.45	$589.40