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	$212.36	13.382%	$240.778	$240.78	$240.80	$240.80
Purchase #2	$134.95	12.451%	$151.7526	$151.75	$151.75	$151.80
Purchase #3	$176.58	11.201%	$196.3587	$196.36	$196.35	$196.40
Purchase #4	$123.88	10.131%	$136.4303	$136.43	$136.45	$136.40
Purchase #5	$23.51	8.383%	$25.4808	$25.48	$25.50	$25.50
Purchase #6	$166.87	13.294%	$189.0537	$189.05	$189.05	$189.10
Purchase #7	$179.80	9.383%	$196.6706	$196.67	$196.65	$196.70
7 purchase totals =	$1,017.95		$1,136.5247	$1,136.52	$1,136.55	$1,136.70