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	$13.38	5.270%	$14.0851	$14.09	$14.10	$14.10
Purchase #2	$15.98	9.697%	$17.5296	$17.53	$17.55	$17.50
Purchase #3	$149.90	7.170%	$160.6478	$160.65	$160.65	$160.60
Purchase #4	$48.94	12.736%	$55.173	$55.17	$55.15	$55.20
Purchase #5	$100.72	10.781%	$111.5786	$111.58	$111.60	$111.60
Purchase #6	$226.60	3.536%	$234.6126	$234.61	$234.60	$234.60
Purchase #7	$166.26	11.806%	$185.8887	$185.89	$185.90	$185.90
7 purchase totals =	$721.78		$779.5154	$779.52	$779.55	$779.50