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	$65.45	3.437%	$67.6995	$67.70	$67.70	$67.70
Purchase #2	$32.95	13.839%	$37.51	$37.51	$37.50	$37.50
Purchase #3	$17.68	10.741%	$19.579	$19.58	$19.60	$19.60
Purchase #4	$98.55	13.778%	$112.1282	$112.13	$112.15	$112.10
Purchase #5	$37.86	13.432%	$42.9454	$42.95	$42.95	$42.90
Purchase #6	$100.27	10.832%	$111.1312	$111.13	$111.15	$111.10
Purchase #7	$62.52	5.216%	$65.781	$65.78	$65.80	$65.80
7 purchase totals =	$415.28		$456.7743	$456.78	$456.85	$456.70