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	$216.37	8.640%	$235.0644	$235.06	$235.05	$235.10
Purchase #2	$116.77	8.146%	$126.2821	$126.28	$126.30	$126.30
Purchase #3	$144.60	7.790%	$155.8643	$155.86	$155.85	$155.90
Purchase #4	$54.53	12.344%	$61.2612	$61.26	$61.25	$61.30
Purchase #5	$75.43	13.867%	$85.8899	$85.89	$85.90	$85.90
Purchase #6	$143.58	10.631%	$158.844	$158.84	$158.85	$158.80
Purchase #7	$248.61	13.236%	$281.516	$281.52	$281.50	$281.50
7 purchase totals =	$999.89		$1,104.7219	$1,104.71	$1,104.70	$1,104.80