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	$101.39	8.130%	$109.633	$109.63	$109.65	$109.60
Purchase #2	$147.60	11.163%	$164.0766	$164.08	$164.10	$164.10
Purchase #3	$74.82	5.303%	$78.7877	$78.79	$78.80	$78.80
Purchase #4	$85.81	5.209%	$90.2798	$90.28	$90.30	$90.30
Purchase #5	$47.65	10.593%	$52.6976	$52.70	$52.70	$52.70
Purchase #6	$105.89	6.451%	$112.721	$112.72	$112.70	$112.70
Purchase #7	$239.31	12.589%	$269.4367	$269.44	$269.45	$269.40
7 purchase totals =	$802.47		$877.6324	$877.64	$877.70	$877.60