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	$41.98	9.230%	$45.8548	$45.85	$45.85	$45.90
Purchase #2	$184.50	3.434%	$190.8357	$190.84	$190.85	$190.80
Purchase #3	$117.73	7.858%	$126.9812	$126.98	$127.00	$127.00
Purchase #4	$72.57	5.582%	$76.6209	$76.62	$76.60	$76.60
Purchase #5	$239.26	6.332%	$254.4099	$254.41	$254.40	$254.40
Purchase #6	$179.49	5.113%	$188.6673	$188.67	$188.65	$188.70
Purchase #7	$153.92	12.686%	$173.4463	$173.45	$173.45	$173.40
7 purchase totals =	$989.45		$1,056.8161	$1,056.82	$1,056.80	$1,056.80