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	$83.85	4.806%	$87.8798	$87.88	$87.90	$87.90
Purchase #2	$55.77	11.440%	$62.1501	$62.15	$62.15	$62.20
Purchase #3	$19.72	3.612%	$20.4323	$20.43	$20.45	$20.40
Purchase #4	$59.71	5.426%	$62.9499	$62.95	$62.95	$62.90
Purchase #5	$42.93	13.383%	$48.6753	$48.68	$48.70	$48.70
Purchase #6	$226.27	3.274%	$233.6781	$233.68	$233.70	$233.70
Purchase #7	$55.27	9.116%	$60.3084	$60.31	$60.30	$60.30
7 purchase totals =	$543.52		$576.0739	$576.08	$576.15	$576.10