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	$210.55	5.660%	$222.4671	$222.47	$222.45	$222.50
Purchase #2	$185.87	7.391%	$199.6077	$199.61	$199.60	$199.60
Purchase #3	$226.45	3.578%	$234.5524	$234.55	$234.55	$234.60
Purchase #4	$51.85	11.509%	$57.8174	$57.82	$57.80	$57.80
Purchase #5	$246.74	3.775%	$256.0544	$256.05	$256.05	$256.10
Purchase #6	$199.26	12.237%	$223.6434	$223.64	$223.65	$223.60
Purchase #7	$92.71	3.852%	$96.2812	$96.28	$96.30	$96.30
7 purchase totals =	$1,213.43		$1,290.4236	$1,290.42	$1,290.40	$1,290.50