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	$151.40	10.156%	$166.7762	$166.78	$166.80	$166.80
Purchase #2	$16.77	10.286%	$18.495	$18.50	$18.50	$18.50
Purchase #3	$11.64	10.261%	$12.8344	$12.83	$12.85	$12.80
Purchase #4	$64.25	13.332%	$72.8158	$72.82	$72.80	$72.80
Purchase #5	$10.64	6.247%	$11.3047	$11.30	$11.30	$11.30
Purchase #6	$76.51	12.612%	$86.1594	$86.16	$86.15	$86.20
Purchase #7	$175.44	12.600%	$197.5454	$197.55	$197.55	$197.50
7 purchase totals =	$506.65		$565.9309	$565.94	$565.95	$565.90