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	$230.75	9.834%	$253.442	$253.44	$253.45	$253.40
Purchase #2	$176.43	7.832%	$190.248	$190.25	$190.25	$190.20
Purchase #3	$80.87	11.866%	$90.466	$90.47	$90.45	$90.50
Purchase #4	$22.40	12.642%	$25.2318	$25.23	$25.25	$25.20
Purchase #5	$149.92	4.671%	$156.9228	$156.92	$156.90	$156.90
Purchase #6	$211.35	3.856%	$219.4997	$219.50	$219.50	$219.50
Purchase #7	$148.64	6.738%	$158.6554	$158.66	$158.65	$158.70
7 purchase totals =	$1,020.36		$1,094.4657	$1,094.47	$1,094.45	$1,094.40