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	$54.42	10.135%	$59.9355	$59.94	$59.95	$59.90
Purchase #2	$132.72	13.610%	$150.7832	$150.78	$150.80	$150.80
Purchase #3	$19.92	5.773%	$21.07	$21.07	$21.05	$21.10
Purchase #4	$127.60	6.608%	$136.0318	$136.03	$136.05	$136.00
Purchase #5	$31.45	4.444%	$32.8476	$32.85	$32.85	$32.80
Purchase #6	$229.72	10.359%	$253.5167	$253.52	$253.50	$253.50
Purchase #7	$107.91	4.264%	$112.5113	$112.51	$112.50	$112.50
7 purchase totals =	$703.74		$766.6961	$766.70	$766.70	$766.60