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	$238.76	9.244%	$260.831	$260.83	$260.85	$260.80
Purchase #2	$237.82	3.867%	$247.0165	$247.02	$247.00	$247.00
Purchase #3	$74.64	5.125%	$78.4653	$78.47	$78.45	$78.50
Purchase #4	$81.39	10.223%	$89.7105	$89.71	$89.70	$89.70
Purchase #5	$144.46	12.667%	$162.7587	$162.76	$162.75	$162.80
Purchase #6	$149.43	4.871%	$156.7087	$156.71	$156.70	$156.70
Purchase #7	$71.27	3.339%	$73.6497	$73.65	$73.65	$73.60
7 purchase totals =	$997.77		$1,069.1404	$1,069.15	$1,069.10	$1,069.10