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	$227.65	7.808%	$245.4249	$245.42	$245.40	$245.40
Purchase #2	$143.77	5.308%	$151.4013	$151.40	$151.40	$151.40
Purchase #3	$44.40	8.435%	$48.1451	$48.15	$48.15	$48.10
Purchase #4	$140.98	8.205%	$152.5474	$152.55	$152.55	$152.50
Purchase #5	$44.60	3.621%	$46.215	$46.22	$46.20	$46.20
Purchase #6	$110.76	11.405%	$123.3922	$123.39	$123.40	$123.40
Purchase #7	$228.26	10.124%	$251.369	$251.37	$251.35	$251.40
7 purchase totals =	$940.42		$1,018.4949	$1,018.50	$1,018.45	$1,018.40