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	$55.66	9.707%	$61.0629	$61.06	$61.05	$61.10
Purchase #2	$9.28	12.660%	$10.4548	$10.45	$10.45	$10.50
Purchase #3	$61.91	9.783%	$67.9667	$67.97	$67.95	$68.00
Purchase #4	$178.99	8.342%	$193.9213	$193.92	$193.90	$193.90
Purchase #5	$20.84	4.723%	$21.8243	$21.82	$21.80	$21.80
Purchase #6	$42.74	6.391%	$45.4715	$45.47	$45.45	$45.50
Purchase #7	$168.53	13.286%	$190.9209	$190.92	$190.90	$190.90
7 purchase totals =	$537.95		$591.6224	$591.61	$591.50	$591.70