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	$173.82	9.291%	$189.9696	$189.97	$189.95	$190.00
Purchase #2	$121.55	4.378%	$126.8715	$126.87	$126.85	$126.90
Purchase #3	$29.26	10.801%	$32.4204	$32.42	$32.40	$32.40
Purchase #4	$48.35	4.245%	$50.4025	$50.40	$50.40	$50.40
Purchase #5	$103.28	7.477%	$111.0022	$111.00	$111.00	$111.00
Purchase #6	$147.40	13.716%	$167.6174	$167.62	$167.60	$167.60
Purchase #7	$59.98	12.516%	$67.4871	$67.49	$67.50	$67.50
7 purchase totals =	$683.64		$745.7707	$745.77	$745.70	$745.80