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	$173.81	8.481%	$188.5508	$188.55	$188.55	$188.60
Purchase #2	$108.95	7.469%	$117.0875	$117.09	$117.10	$117.10
Purchase #3	$11.50	4.446%	$12.0113	$12.01	$12.00	$12.00
Purchase #4	$180.85	6.455%	$192.5239	$192.52	$192.50	$192.50
Purchase #5	$179.65	5.104%	$188.8193	$188.82	$188.80	$188.80
Purchase #6	$239.94	4.659%	$251.1188	$251.12	$251.10	$251.10
Purchase #7	$101.69	9.548%	$111.3994	$111.40	$111.40	$111.40
7 purchase totals =	$996.39		$1,061.5110	$1,061.51	$1,061.45	$1,061.50