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	$243.63	5.763%	$257.6704	$257.67	$257.65	$257.70
Purchase #2	$53.64	7.360%	$57.5879	$57.59	$57.60	$57.60
Purchase #3	$19.32	9.149%	$21.0876	$21.09	$21.10	$21.10
Purchase #4	$64.75	9.794%	$71.0916	$71.09	$71.10	$71.10
Purchase #5	$96.52	9.441%	$105.6325	$105.63	$105.65	$105.60
Purchase #6	$117.39	8.796%	$127.7156	$127.72	$127.70	$127.70
Purchase #7	$235.34	8.443%	$255.2098	$255.21	$255.20	$255.20
7 purchase totals =	$830.59		$895.9954	$896.00	$896.00	$896.00