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	$39.40	12.105%	$44.1694	$44.17	$44.15	$44.20
Purchase #2	$101.73	3.622%	$105.4147	$105.41	$105.40	$105.40
Purchase #3	$172.82	10.117%	$190.3042	$190.30	$190.30	$190.30
Purchase #4	$169.38	9.460%	$185.4033	$185.40	$185.40	$185.40
Purchase #5	$108.75	10.783%	$120.4765	$120.48	$120.50	$120.50
Purchase #6	$105.64	5.515%	$111.466	$111.47	$111.45	$111.50
Purchase #7	$66.30	4.161%	$69.0587	$69.06	$69.05	$69.10
7 purchase totals =	$764.02		$826.2928	$826.29	$826.25	$826.40