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	$231.59	9.294%	$253.114	$253.11	$253.10	$253.10
Purchase #2	$75.55	4.389%	$78.8659	$78.87	$78.85	$78.90
Purchase #3	$52.57	13.827%	$59.8389	$59.84	$59.85	$59.80
Purchase #4	$164.50	5.737%	$173.9374	$173.94	$173.95	$173.90
Purchase #5	$177.37	7.106%	$189.9739	$189.97	$189.95	$190.00
Purchase #6	$205.25	12.268%	$230.4301	$230.43	$230.45	$230.40
Purchase #7	$146.61	13.104%	$165.8218	$165.82	$165.80	$165.80
7 purchase totals =	$1,053.44		$1,151.9820	$1,151.98	$1,151.95	$1,151.90