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	$200.70	5.561%	$211.8609	$211.86	$211.85	$211.90
Purchase #2	$227.43	6.580%	$242.3949	$242.39	$242.40	$242.40
Purchase #3	$107.58	3.635%	$111.4905	$111.49	$111.50	$111.50
Purchase #4	$185.75	5.847%	$196.6108	$196.61	$196.60	$196.60
Purchase #5	$244.70	13.303%	$277.2524	$277.25	$277.25	$277.30
Purchase #6	$37.58	8.470%	$40.763	$40.76	$40.75	$40.80
Purchase #7	$81.37	10.715%	$90.0888	$90.09	$90.10	$90.10
7 purchase totals =	$1,085.11		$1,170.4613	$1,170.45	$1,170.45	$1,170.60