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	$144.43	9.588%	$158.2779	$158.28	$158.30	$158.30
Purchase #2	$185.97	10.584%	$205.6531	$205.65	$205.65	$205.70
Purchase #3	$146.43	6.821%	$156.418	$156.42	$156.40	$156.40
Purchase #4	$100.46	10.574%	$111.0826	$111.08	$111.10	$111.10
Purchase #5	$91.39	5.521%	$96.4356	$96.44	$96.45	$96.40
Purchase #6	$154.27	10.360%	$170.2524	$170.25	$170.25	$170.30
Purchase #7	$69.41	10.724%	$76.8535	$76.85	$76.85	$76.90
7 purchase totals =	$892.36		$974.9731	$974.97	$975.00	$975.10