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	$214.31	5.601%	$226.3135	$226.31	$226.30	$226.30
Purchase #2	$52.43	3.367%	$54.1953	$54.20	$54.20	$54.20
Purchase #3	$137.30	12.618%	$154.6245	$154.62	$154.60	$154.60
Purchase #4	$41.99	3.841%	$43.6028	$43.60	$43.60	$43.60
Purchase #5	$181.52	3.430%	$187.7461	$187.75	$187.75	$187.70
Purchase #6	$120.89	10.198%	$133.2184	$133.22	$133.20	$133.20
Purchase #7	$229.86	11.105%	$255.386	$255.39	$255.40	$255.40
7 purchase totals =	$978.30		$1,055.0866	$1,055.09	$1,055.05	$1,055.00