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	$155.50	11.232%	$172.9658	$172.97	$172.95	$173.00
Purchase #2	$30.30	10.551%	$33.497	$33.50	$33.50	$33.50
Purchase #3	$49.83	10.120%	$54.8728	$54.87	$54.85	$54.90
Purchase #4	$40.65	4.547%	$42.4984	$42.50	$42.50	$42.50
Purchase #5	$34.32	5.174%	$36.0957	$36.10	$36.10	$36.10
Purchase #6	$40.78	5.311%	$42.9458	$42.95	$42.95	$42.90
Purchase #7	$171.85	6.574%	$183.1474	$183.15	$183.15	$183.10
7 purchase totals =	$523.23		$566.0229	$566.04	$566.00	$566.00