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	$173.62	5.238%	$182.7142	$182.71	$182.70	$182.70
Purchase #2	$49.83	11.521%	$55.5709	$55.57	$55.55	$55.60
Purchase #3	$54.74	8.559%	$59.4252	$59.43	$59.45	$59.40
Purchase #4	$75.41	9.587%	$82.6396	$82.64	$82.65	$82.60
Purchase #5	$108.74	7.493%	$116.8879	$116.89	$116.90	$116.90
Purchase #6	$101.62	11.363%	$113.1671	$113.17	$113.15	$113.20
Purchase #7	$117.73	13.466%	$133.5835	$133.58	$133.60	$133.60
7 purchase totals =	$681.69		$743.9884	$743.99	$744.00	$744.00