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	$217.82	4.692%	$228.0401	$228.04	$228.05	$228.00
Purchase #2	$165.33	4.812%	$173.2857	$173.29	$173.30	$173.30
Purchase #3	$103.72	7.227%	$111.2158	$111.22	$111.20	$111.20
Purchase #4	$37.94	12.442%	$42.6605	$42.66	$42.65	$42.70
Purchase #5	$40.70	7.733%	$43.8473	$43.85	$43.85	$43.80
Purchase #6	$89.53	6.761%	$95.5831	$95.58	$95.60	$95.60
Purchase #7	$188.42	8.664%	$204.7447	$204.74	$204.75	$204.70
7 purchase totals =	$843.46		$899.3772	$899.38	$899.40	$899.30