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	$143.98	7.268%	$154.4445	$154.44	$154.45	$154.40
Purchase #2	$114.69	11.105%	$127.4263	$127.43	$127.45	$127.40
Purchase #3	$19.81	6.798%	$21.1567	$21.16	$21.15	$21.20
Purchase #4	$112.72	4.509%	$117.8025	$117.80	$117.80	$117.80
Purchase #5	$208.47	6.713%	$222.4646	$222.46	$222.45	$222.50
Purchase #6	$219.70	4.181%	$228.8857	$228.89	$228.90	$228.90
Purchase #7	$224.98	10.740%	$249.1429	$249.14	$249.15	$249.10
7 purchase totals =	$1,044.35		$1,121.3232	$1,121.32	$1,121.35	$1,121.30