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	$247.98	9.725%	$272.0961	$272.10	$272.10	$272.10
Purchase #2	$93.75	13.758%	$106.6481	$106.65	$106.65	$106.60
Purchase #3	$185.87	5.643%	$196.3586	$196.36	$196.35	$196.40
Purchase #4	$108.50	5.618%	$114.5955	$114.60	$114.60	$114.60
Purchase #5	$9.68	9.428%	$10.5926	$10.59	$10.60	$10.60
Purchase #6	$142.39	9.555%	$155.9954	$156.00	$156.00	$156.00
Purchase #7	$242.43	12.145%	$271.8731	$271.87	$271.85	$271.90
7 purchase totals =	$1,030.60		$1,128.1594	$1,128.17	$1,128.15	$1,128.20