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	$215.68	6.549%	$229.8049	$229.80	$229.80	$229.80
Purchase #2	$87.87	3.156%	$90.6432	$90.64	$90.65	$90.60
Purchase #3	$212.71	3.162%	$219.4359	$219.44	$219.45	$219.40
Purchase #4	$9.92	10.181%	$10.93	$10.93	$10.95	$10.90
Purchase #5	$249.25	4.643%	$260.8227	$260.82	$260.80	$260.80
Purchase #6	$142.89	13.532%	$162.2259	$162.23	$162.25	$162.20
Purchase #7	$41.46	6.613%	$44.2017	$44.20	$44.20	$44.20
7 purchase totals =	$959.78		$1,018.0643	$1,018.06	$1,018.10	$1,017.90