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	$247.96	13.514%	$281.4693	$281.47	$281.45	$281.50
Purchase #2	$132.58	9.430%	$145.0823	$145.08	$145.10	$145.10
Purchase #3	$196.95	4.559%	$205.929	$205.93	$205.95	$205.90
Purchase #4	$18.39	6.572%	$19.5986	$19.60	$19.60	$19.60
Purchase #5	$78.76	12.512%	$88.6145	$88.61	$88.60	$88.60
Purchase #6	$133.95	6.485%	$142.6367	$142.64	$142.65	$142.60
Purchase #7	$150.70	10.532%	$166.5717	$166.57	$166.55	$166.60
7 purchase totals =	$959.29		$1,049.9021	$1,049.90	$1,049.90	$1,049.90