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	$171.71	6.706%	$183.2249	$183.22	$183.20	$183.20
Purchase #2	$82.49	8.707%	$89.6724	$89.67	$89.65	$89.70
Purchase #3	$190.72	8.846%	$207.5911	$207.59	$207.60	$207.60
Purchase #4	$10.76	6.360%	$11.4443	$11.44	$11.45	$11.40
Purchase #5	$148.47	4.837%	$155.6515	$155.65	$155.65	$155.70
Purchase #6	$175.71	11.225%	$195.4334	$195.43	$195.45	$195.40
Purchase #7	$158.61	9.277%	$173.3242	$173.32	$173.30	$173.30
7 purchase totals =	$938.47		$1,016.3418	$1,016.32	$1,016.30	$1,016.30