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	$168.92	11.799%	$188.8509	$188.85	$188.85	$188.90
Purchase #2	$101.68	10.579%	$112.4367	$112.44	$112.45	$112.40
Purchase #3	$155.97	10.315%	$172.0583	$172.06	$172.05	$172.10
Purchase #4	$131.79	4.595%	$137.8458	$137.85	$137.85	$137.80
Purchase #5	$177.25	4.707%	$185.5932	$185.59	$185.60	$185.60
Purchase #6	$209.41	5.407%	$220.7328	$220.73	$220.75	$220.70
Purchase #7	$44.57	11.377%	$49.6407	$49.64	$49.65	$49.60
7 purchase totals =	$989.59		$1,067.1584	$1,067.16	$1,067.20	$1,067.10