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	$127.32	13.108%	$144.0091	$144.01	$144.00	$144.00
Purchase #2	$151.45	10.621%	$167.5355	$167.54	$167.55	$167.50
Purchase #3	$18.69	3.335%	$19.3133	$19.31	$19.30	$19.30
Purchase #4	$230.58	6.754%	$246.1534	$246.15	$246.15	$246.20
Purchase #5	$39.26	10.686%	$43.4553	$43.46	$43.45	$43.50
Purchase #6	$5.51	13.666%	$6.263	$6.26	$6.25	$6.30
Purchase #7	$55.99	10.189%	$61.6948	$61.69	$61.70	$61.70
7 purchase totals =	$628.80		$688.4244	$688.42	$688.40	$688.50