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	$163.56	5.462%	$172.4936	$172.49	$172.50	$172.50
Purchase #2	$9.25	11.491%	$10.3129	$10.31	$10.30	$10.30
Purchase #3	$217.87	10.445%	$240.6265	$240.63	$240.65	$240.60
Purchase #4	$170.64	8.471%	$185.0949	$185.09	$185.10	$185.10
Purchase #5	$107.99	11.552%	$120.465	$120.47	$120.45	$120.50
Purchase #6	$210.88	10.538%	$233.1025	$233.10	$233.10	$233.10
Purchase #7	$175.58	7.245%	$188.3008	$188.30	$188.30	$188.30
7 purchase totals =	$1,055.77		$1,150.3962	$1,150.39	$1,150.40	$1,150.40