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	$106.27	5.599%	$112.2201	$112.22	$112.20	$112.20
Purchase #2	$208.48	5.784%	$220.5385	$220.54	$220.55	$220.50
Purchase #3	$23.59	6.238%	$25.0615	$25.06	$25.05	$25.10
Purchase #4	$242.35	12.771%	$273.3005	$273.30	$273.30	$273.30
Purchase #5	$192.49	4.211%	$200.5958	$200.60	$200.60	$200.60
Purchase #6	$49.52	9.793%	$54.3695	$54.37	$54.35	$54.40
Purchase #7	$158.90	13.123%	$179.7524	$179.75	$179.75	$179.80
7 purchase totals =	$981.60		$1,065.8383	$1,065.84	$1,065.80	$1,065.90