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	$107.97	8.140%	$116.7588	$116.76	$116.75	$116.80
Purchase #2	$36.53	9.724%	$40.0822	$40.08	$40.10	$40.10
Purchase #3	$221.90	5.722%	$234.5971	$234.60	$234.60	$234.60
Purchase #4	$105.50	5.377%	$111.1727	$111.17	$111.15	$111.20
Purchase #5	$187.92	5.241%	$197.7689	$197.77	$197.75	$197.80
Purchase #6	$139.64	8.521%	$151.5387	$151.54	$151.55	$151.50
Purchase #7	$50.79	9.293%	$55.5099	$55.51	$55.50	$55.50
7 purchase totals =	$850.25		$907.4283	$907.43	$907.40	$907.50