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	$157.32	7.704%	$169.4399	$169.44	$169.45	$169.40
Purchase #2	$108.43	5.583%	$114.4836	$114.48	$114.50	$114.50
Purchase #3	$105.27	5.663%	$111.2314	$111.23	$111.25	$111.20
Purchase #4	$231.60	11.776%	$258.8732	$258.87	$258.85	$258.90
Purchase #5	$10.70	12.172%	$12.0024	$12.00	$12.00	$12.00
Purchase #6	$48.70	12.369%	$54.7237	$54.72	$54.70	$54.70
Purchase #7	$72.97	5.380%	$76.8958	$76.90	$76.90	$76.90
7 purchase totals =	$734.99		$797.6500	$797.64	$797.65	$797.60