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	$52.40	3.353%	$54.157	$54.16	$54.15	$54.20
Purchase #2	$92.42	8.631%	$100.3968	$100.40	$100.40	$100.40
Purchase #3	$153.74	8.874%	$167.3829	$167.38	$167.40	$167.40
Purchase #4	$138.39	9.677%	$151.782	$151.78	$151.80	$151.80
Purchase #5	$29.50	5.353%	$31.0791	$31.08	$31.10	$31.10
Purchase #6	$243.84	7.538%	$262.2207	$262.22	$262.20	$262.20
Purchase #7	$9.60	13.357%	$10.8823	$10.88	$10.90	$10.90
7 purchase totals =	$719.89		$777.9008	$777.90	$777.95	$778.00