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	$118.87	12.581%	$133.825	$133.83	$133.85	$133.80
Purchase #2	$17.60	8.526%	$19.1006	$19.10	$19.10	$19.10
Purchase #3	$61.89	5.657%	$65.3911	$65.39	$65.40	$65.40
Purchase #4	$120.60	11.634%	$134.6306	$134.63	$134.65	$134.60
Purchase #5	$142.92	10.589%	$158.0538	$158.05	$158.05	$158.10
Purchase #6	$18.73	12.839%	$21.1347	$21.13	$21.15	$21.10
Purchase #7	$81.28	6.857%	$86.8534	$86.85	$86.85	$86.90
7 purchase totals =	$561.89		$618.9892	$618.98	$619.05	$619.00