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	$79.53	11.856%	$88.9591	$88.96	$88.95	$89.00
Purchase #2	$109.97	13.289%	$124.5839	$124.58	$124.60	$124.60
Purchase #3	$12.51	4.395%	$13.0598	$13.06	$13.05	$13.10
Purchase #4	$68.72	13.426%	$77.9463	$77.95	$77.95	$77.90
Purchase #5	$85.89	11.596%	$95.8498	$95.85	$95.85	$95.80
Purchase #6	$197.56	5.719%	$208.8585	$208.86	$208.85	$208.90
Purchase #7	$176.43	11.393%	$196.5307	$196.53	$196.55	$196.50
7 purchase totals =	$730.61		$805.7881	$805.79	$805.80	$805.80