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	$23.51	9.771%	$25.8072	$25.81	$25.80	$25.80
Purchase #2	$107.97	11.834%	$120.7472	$120.75	$120.75	$120.70
Purchase #3	$59.63	8.409%	$64.6443	$64.64	$64.65	$64.60
Purchase #4	$67.39	5.401%	$71.0297	$71.03	$71.05	$71.00
Purchase #5	$93.69	7.669%	$100.8751	$100.88	$100.90	$100.90
Purchase #6	$33.60	11.849%	$37.5813	$37.58	$37.60	$37.60
Purchase #7	$143.40	10.499%	$158.4556	$158.46	$158.45	$158.50
7 purchase totals =	$529.19		$579.1404	$579.15	$579.20	$579.10