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	$26.55	6.517%	$28.2803	$28.28	$28.30	$28.30
Purchase #2	$27.80	3.573%	$28.7933	$28.79	$28.80	$28.80
Purchase #3	$122.66	4.212%	$127.8264	$127.83	$127.85	$127.80
Purchase #4	$149.32	4.107%	$155.4526	$155.45	$155.45	$155.50
Purchase #5	$139.63	8.514%	$151.5181	$151.52	$151.50	$151.50
Purchase #6	$183.39	9.451%	$200.7222	$200.72	$200.70	$200.70
Purchase #7	$152.87	11.147%	$169.9104	$169.91	$169.90	$169.90
7 purchase totals =	$802.22		$862.5033	$862.50	$862.50	$862.50