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	$12.29	13.586%	$13.9597	$13.96	$13.95	$14.00
Purchase #2	$56.84	4.861%	$59.603	$59.60	$59.60	$59.60
Purchase #3	$222.39	4.245%	$231.8305	$231.83	$231.85	$231.80
Purchase #4	$156.44	11.631%	$174.6355	$174.64	$174.65	$174.60
Purchase #5	$120.98	13.457%	$137.2603	$137.26	$137.25	$137.30
Purchase #6	$106.83	9.162%	$116.6178	$116.62	$116.60	$116.60
Purchase #7	$73.52	13.591%	$83.5121	$83.51	$83.50	$83.50
7 purchase totals =	$749.29		$817.4189	$817.42	$817.40	$817.40