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	$64.34	12.836%	$72.5987	$72.60	$72.60	$72.60
Purchase #2	$148.75	4.415%	$155.3173	$155.32	$155.30	$155.30
Purchase #3	$131.52	9.149%	$143.5528	$143.55	$143.55	$143.60
Purchase #4	$215.43	8.397%	$233.5197	$233.52	$233.50	$233.50
Purchase #5	$8.62	9.232%	$9.4158	$9.42	$9.40	$9.40
Purchase #6	$61.52	4.679%	$64.3985	$64.40	$64.40	$64.40
Purchase #7	$62.29	3.155%	$64.2552	$64.26	$64.25	$64.30
7 purchase totals =	$692.47		$743.0580	$743.07	$743.00	$743.10