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	$95.45	10.802%	$105.7605	$105.76	$105.75	$105.80
Purchase #2	$37.94	9.533%	$41.5568	$41.56	$41.55	$41.60
Purchase #3	$61.90	7.653%	$66.6372	$66.64	$66.65	$66.60
Purchase #4	$96.28	6.241%	$102.2888	$102.29	$102.30	$102.30
Purchase #5	$138.93	13.773%	$158.0648	$158.06	$158.05	$158.10
Purchase #6	$59.63	9.706%	$65.4177	$65.42	$65.40	$65.40
Purchase #7	$44.60	11.177%	$49.5849	$49.58	$49.60	$49.60
7 purchase totals =	$534.73		$589.3107	$589.31	$589.30	$589.40