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	$48.35	13.126%	$54.6964	$54.70	$54.70	$54.70
Purchase #2	$151.46	8.742%	$164.7006	$164.70	$164.70	$164.70
Purchase #3	$106.62	11.502%	$118.8834	$118.88	$118.90	$118.90
Purchase #4	$48.52	9.298%	$53.0314	$53.03	$53.05	$53.00
Purchase #5	$44.91	12.676%	$50.6028	$50.60	$50.60	$50.60
Purchase #6	$116.77	9.498%	$127.8608	$127.86	$127.85	$127.90
Purchase #7	$49.64	13.665%	$56.4233	$56.42	$56.40	$56.40
7 purchase totals =	$566.27		$626.1987	$626.19	$626.20	$626.20