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	$74.94	13.748%	$85.2428	$85.24	$85.25	$85.20
Purchase #2	$153.44	13.208%	$173.7064	$173.71	$173.70	$173.70
Purchase #3	$93.67	7.687%	$100.8704	$100.87	$100.85	$100.90
Purchase #4	$45.25	6.144%	$48.0302	$48.03	$48.05	$48.00
Purchase #5	$50.42	11.589%	$56.2632	$56.26	$56.25	$56.30
Purchase #6	$41.41	10.616%	$45.8061	$45.81	$45.80	$45.80
Purchase #7	$98.45	8.114%	$106.4382	$106.44	$106.45	$106.40
7 purchase totals =	$557.58		$616.3573	$616.36	$616.35	$616.30