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	$105.58	10.395%	$116.555	$116.56	$116.55	$116.60
Purchase #2	$151.74	8.437%	$164.5423	$164.54	$164.55	$164.50
Purchase #3	$56.83	8.346%	$61.573	$61.57	$61.55	$61.60
Purchase #4	$139.59	13.658%	$158.6552	$158.66	$158.65	$158.70
Purchase #5	$43.42	10.555%	$48.003	$48.00	$48.00	$48.00
Purchase #6	$117.80	12.581%	$132.6204	$132.62	$132.60	$132.60
Purchase #7	$57.34	9.458%	$62.7632	$62.76	$62.75	$62.80
7 purchase totals =	$672.30		$744.7121	$744.71	$744.65	$744.80