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	$82.96	3.553%	$85.9076	$85.91	$85.90	$85.90
Purchase #2	$13.96	10.643%	$15.4458	$15.45	$15.45	$15.40
Purchase #3	$235.65	10.125%	$259.5096	$259.51	$259.50	$259.50
Purchase #4	$48.39	9.409%	$52.943	$52.94	$52.95	$52.90
Purchase #5	$97.91	5.291%	$103.0904	$103.09	$103.10	$103.10
Purchase #6	$85.69	12.437%	$96.3473	$96.35	$96.35	$96.30
Purchase #7	$130.58	6.765%	$139.4137	$139.41	$139.40	$139.40
7 purchase totals =	$695.14		$752.6574	$752.66	$752.65	$752.50