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	$154.72	5.310%	$162.9356	$162.94	$162.95	$162.90
Purchase #2	$7.66	10.636%	$8.4747	$8.47	$8.45	$8.50
Purchase #3	$132.60	3.449%	$137.1734	$137.17	$137.15	$137.20
Purchase #4	$55.76	12.773%	$62.8822	$62.88	$62.90	$62.90
Purchase #5	$150.68	5.189%	$158.4988	$158.50	$158.50	$158.50
Purchase #6	$16.80	4.380%	$17.5358	$17.54	$17.55	$17.50
Purchase #7	$79.95	13.469%	$90.7185	$90.72	$90.70	$90.70
7 purchase totals =	$598.17		$638.2190	$638.22	$638.20	$638.20