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	$122.49	3.733%	$127.0626	$127.06	$127.05	$127.10
Purchase #2	$217.72	5.155%	$228.9435	$228.94	$228.95	$228.90
Purchase #3	$95.33	8.419%	$103.3558	$103.36	$103.35	$103.40
Purchase #4	$43.99	3.164%	$45.3818	$45.38	$45.40	$45.40
Purchase #5	$158.71	6.141%	$168.4564	$168.46	$168.45	$168.50
Purchase #6	$206.70	7.226%	$221.6361	$221.64	$221.65	$221.60
Purchase #7	$142.56	5.493%	$150.3908	$150.39	$150.40	$150.40
7 purchase totals =	$987.50		$1,045.2270	$1,045.23	$1,045.25	$1,045.30