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	$95.51	10.620%	$105.6532	$105.65	$105.65	$105.70
Purchase #2	$122.63	3.448%	$126.8583	$126.86	$126.85	$126.90
Purchase #3	$111.55	12.543%	$125.5417	$125.54	$125.55	$125.50
Purchase #4	$146.44	3.485%	$151.5434	$151.54	$151.55	$151.50
Purchase #5	$153.44	12.716%	$172.9514	$172.95	$172.95	$173.00
Purchase #6	$114.28	3.707%	$118.5164	$118.52	$118.50	$118.50
Purchase #7	$190.39	4.253%	$198.4873	$198.49	$198.50	$198.50
7 purchase totals =	$934.24		$999.5517	$999.55	$999.55	$999.60