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	$61.82	11.413%	$68.8755	$68.88	$68.90	$68.90
Purchase #2	$52.31	3.748%	$54.2706	$54.27	$54.25	$54.30
Purchase #3	$62.84	10.609%	$69.5067	$69.51	$69.50	$69.50
Purchase #4	$39.60	12.431%	$44.5227	$44.52	$44.50	$44.50
Purchase #5	$181.30	4.770%	$189.948	$189.95	$189.95	$189.90
Purchase #6	$173.66	6.307%	$184.6127	$184.61	$184.60	$184.60
Purchase #7	$11.40	13.143%	$12.8983	$12.90	$12.90	$12.90
7 purchase totals =	$582.93		$624.6345	$624.64	$624.60	$624.60