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	$101.41	8.295%	$109.822	$109.82	$109.80	$109.80
Purchase #2	$176.65	10.787%	$195.7052	$195.71	$195.70	$195.70
Purchase #3	$153.54	7.486%	$165.034	$165.03	$165.05	$165.00
Purchase #4	$128.31	4.632%	$134.2533	$134.25	$134.25	$134.30
Purchase #5	$213.35	6.379%	$226.9596	$226.96	$226.95	$227.00
Purchase #6	$126.80	13.707%	$144.1805	$144.18	$144.20	$144.20
Purchase #7	$100.29	10.805%	$111.1263	$111.13	$111.15	$111.10
7 purchase totals =	$1,000.35		$1,087.0809	$1,087.08	$1,087.10	$1,087.10