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	$106.69	5.562%	$112.6241	$112.62	$112.60	$112.60
Purchase #2	$217.82	5.829%	$230.5167	$230.52	$230.50	$230.50
Purchase #3	$231.25	13.454%	$262.3624	$262.36	$262.35	$262.40
Purchase #4	$229.42	8.864%	$249.7558	$249.76	$249.75	$249.80
Purchase #5	$123.61	11.189%	$137.4407	$137.44	$137.45	$137.40
Purchase #6	$156.58	9.269%	$171.0934	$171.09	$171.10	$171.10
Purchase #7	$54.89	7.699%	$59.116	$59.12	$59.10	$59.10
7 purchase totals =	$1,120.26		$1,222.9091	$1,222.91	$1,222.85	$1,222.90