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	$165.39	11.162%	$183.8508	$183.85	$183.85	$183.90
Purchase #2	$228.81	11.769%	$255.7386	$255.74	$255.75	$255.70
Purchase #3	$122.57	9.283%	$133.9482	$133.95	$133.95	$133.90
Purchase #4	$122.94	5.156%	$129.2788	$129.28	$129.30	$129.30
Purchase #5	$100.58	11.820%	$112.4686	$112.47	$112.45	$112.50
Purchase #6	$42.51	13.145%	$48.0979	$48.10	$48.10	$48.10
Purchase #7	$186.98	5.121%	$196.5552	$196.56	$196.55	$196.60
7 purchase totals =	$969.78		$1,059.9381	$1,059.95	$1,059.95	$1,060.00