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	$34.45	7.625%	$37.0768	$37.08	$37.10	$37.10
Purchase #2	$95.84	4.826%	$100.4652	$100.47	$100.45	$100.50
Purchase #3	$105.59	5.831%	$111.747	$111.75	$111.75	$111.70
Purchase #4	$135.66	11.453%	$151.1971	$151.20	$151.20	$151.20
Purchase #5	$74.72	5.180%	$78.5905	$78.59	$78.60	$78.60
Purchase #6	$61.55	4.307%	$64.201	$64.20	$64.20	$64.20
Purchase #7	$72.89	7.255%	$78.1782	$78.18	$78.20	$78.20
7 purchase totals =	$580.70		$621.4558	$621.47	$621.50	$621.50