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	$158.38	9.828%	$173.9456	$173.95	$173.95	$173.90
Purchase #2	$71.32	9.758%	$78.2794	$78.28	$78.30	$78.30
Purchase #3	$76.29	8.299%	$82.6213	$82.62	$82.60	$82.60
Purchase #4	$56.98	4.582%	$59.5908	$59.59	$59.60	$59.60
Purchase #5	$21.82	13.857%	$24.8436	$24.84	$24.85	$24.80
Purchase #6	$20.79	5.108%	$21.852	$21.85	$21.85	$21.90
Purchase #7	$145.33	5.717%	$153.6385	$153.64	$153.65	$153.60
7 purchase totals =	$550.91		$594.7712	$594.77	$594.80	$594.70