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	$39.74	10.401%	$43.8734	$43.87	$43.85	$43.90
Purchase #2	$129.33	10.794%	$143.2899	$143.29	$143.30	$143.30
Purchase #3	$131.25	10.436%	$144.9473	$144.95	$144.95	$144.90
Purchase #4	$11.41	4.672%	$11.9431	$11.94	$11.95	$11.90
Purchase #5	$156.36	10.412%	$172.6402	$172.64	$172.65	$172.60
Purchase #6	$227.70	12.417%	$255.9735	$255.97	$255.95	$256.00
Purchase #7	$223.78	10.445%	$247.1538	$247.15	$247.15	$247.20
7 purchase totals =	$919.57		$1,019.8212	$1,019.81	$1,019.80	$1,019.80