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	$49.50	10.294%	$54.5955	$54.60	$54.60	$54.60
Purchase #2	$39.61	11.232%	$44.059	$44.06	$44.05	$44.10
Purchase #3	$221.90	8.192%	$240.078	$240.08	$240.10	$240.10
Purchase #4	$145.30	5.681%	$153.5545	$153.55	$153.55	$153.60
Purchase #5	$201.33	10.395%	$222.2583	$222.26	$222.25	$222.30
Purchase #6	$244.59	3.322%	$252.7153	$252.72	$252.70	$252.70
Purchase #7	$133.48	13.463%	$151.4504	$151.45	$151.45	$151.50
7 purchase totals =	$1,035.71		$1,118.7110	$1,118.72	$1,118.70	$1,118.90