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	$88.90	4.672%	$93.0534	$93.05	$93.05	$93.10
Purchase #2	$127.66	13.527%	$144.9286	$144.93	$144.95	$144.90
Purchase #3	$47.65	13.531%	$54.0975	$54.10	$54.10	$54.10
Purchase #4	$140.32	8.195%	$151.8192	$151.82	$151.80	$151.80
Purchase #5	$172.62	5.349%	$181.8534	$181.85	$181.85	$181.90
Purchase #6	$118.92	11.765%	$132.9109	$132.91	$132.90	$132.90
Purchase #7	$216.45	11.467%	$241.2703	$241.27	$241.25	$241.30
7 purchase totals =	$912.52		$999.9333	$999.93	$999.90	$1,000.00