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	$132.64	8.165%	$143.4701	$143.47	$143.45	$143.50
Purchase #2	$101.68	9.575%	$111.4159	$111.42	$111.40	$111.40
Purchase #3	$128.53	4.307%	$134.0658	$134.07	$134.05	$134.10
Purchase #4	$166.59	11.162%	$185.1848	$185.18	$185.20	$185.20
Purchase #5	$83.26	6.848%	$88.9616	$88.96	$88.95	$89.00
Purchase #6	$94.31	11.470%	$105.1274	$105.13	$105.15	$105.10
Purchase #7	$115.72	6.373%	$123.0948	$123.09	$123.10	$123.10
7 purchase totals =	$822.73		$891.3204	$891.32	$891.30	$891.40