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	$129.66	12.836%	$146.3032	$146.30	$146.30	$146.30
Purchase #2	$122.40	12.784%	$138.0476	$138.05	$138.05	$138.00
Purchase #3	$153.47	3.347%	$158.6066	$158.61	$158.60	$158.60
Purchase #4	$28.27	6.690%	$30.1613	$30.16	$30.15	$30.20
Purchase #5	$104.44	6.748%	$111.4876	$111.49	$111.50	$111.50
Purchase #6	$88.68	13.111%	$100.3068	$100.31	$100.30	$100.30
Purchase #7	$169.31	4.128%	$176.2991	$176.30	$176.30	$176.30
7 purchase totals =	$796.23		$861.2122	$861.22	$861.20	$861.20