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	$160.88	11.838%	$179.925	$179.93	$179.95	$179.90
Purchase #2	$55.58	10.827%	$61.5976	$61.60	$61.60	$61.60
Purchase #3	$39.72	13.866%	$45.2276	$45.23	$45.25	$45.20
Purchase #4	$221.56	3.804%	$229.9881	$229.99	$230.00	$230.00
Purchase #5	$49.30	12.723%	$55.5724	$55.57	$55.55	$55.60
Purchase #6	$244.29	4.598%	$255.5225	$255.52	$255.50	$255.50
Purchase #7	$58.77	5.590%	$62.0552	$62.06	$62.05	$62.10
7 purchase totals =	$830.10		$889.8884	$889.90	$889.90	$889.90