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	$41.78	4.301%	$43.577	$43.58	$43.60	$43.60
Purchase #2	$66.90	9.328%	$73.1404	$73.14	$73.15	$73.10
Purchase #3	$100.50	8.431%	$108.9732	$108.97	$108.95	$109.00
Purchase #4	$191.53	13.845%	$218.0473	$218.05	$218.05	$218.00
Purchase #5	$103.43	12.579%	$116.4405	$116.44	$116.45	$116.40
Purchase #6	$148.27	10.153%	$163.3239	$163.32	$163.30	$163.30
Purchase #7	$154.32	11.710%	$172.3909	$172.39	$172.40	$172.40
7 purchase totals =	$806.73		$895.8932	$895.89	$895.90	$895.80