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	$79.50	7.512%	$85.472	$85.47	$85.45	$85.50
Purchase #2	$48.82	8.329%	$52.8862	$52.89	$52.90	$52.90
Purchase #3	$212.39	8.683%	$230.8318	$230.83	$230.85	$230.80
Purchase #4	$43.76	10.707%	$48.4454	$48.45	$48.45	$48.40
Purchase #5	$185.43	6.523%	$197.5256	$197.53	$197.55	$197.50
Purchase #6	$245.43	3.416%	$253.8139	$253.81	$253.80	$253.80
Purchase #7	$158.68	5.485%	$167.3836	$167.38	$167.40	$167.40
7 purchase totals =	$974.01		$1,036.3585	$1,036.36	$1,036.40	$1,036.30