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	$11.33	9.436%	$12.3991	$12.40	$12.40	$12.40
Purchase #2	$190.32	12.757%	$214.5991	$214.60	$214.60	$214.60
Purchase #3	$163.90	4.720%	$171.6361	$171.64	$171.65	$171.60
Purchase #4	$16.64	8.450%	$18.0461	$18.05	$18.05	$18.00
Purchase #5	$11.72	4.500%	$12.2474	$12.25	$12.25	$12.20
Purchase #6	$72.50	8.829%	$78.901	$78.90	$78.90	$78.90
Purchase #7	$205.60	11.668%	$229.5894	$229.59	$229.60	$229.60
7 purchase totals =	$672.01		$737.4182	$737.43	$737.45	$737.30