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	$66.51	5.461%	$70.1421	$70.14	$70.15	$70.10
Purchase #2	$237.72	6.494%	$253.1575	$253.16	$253.15	$253.20
Purchase #3	$20.40	7.551%	$21.9404	$21.94	$21.95	$21.90
Purchase #4	$150.47	7.733%	$162.1058	$162.11	$162.10	$162.10
Purchase #5	$250.64	9.438%	$274.2954	$274.30	$274.30	$274.30
Purchase #6	$104.84	6.660%	$111.8223	$111.82	$111.80	$111.80
Purchase #7	$129.39	13.291%	$146.5872	$146.59	$146.60	$146.60
7 purchase totals =	$959.97		$1,040.0507	$1,040.06	$1,040.05	$1,040.00