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	$59.26	13.169%	$67.0639	$67.06	$67.05	$67.10
Purchase #2	$91.64	9.417%	$100.2697	$100.27	$100.25	$100.30
Purchase #3	$50.30	11.210%	$55.9386	$55.94	$55.95	$55.90
Purchase #4	$145.60	7.495%	$156.5127	$156.51	$156.50	$156.50
Purchase #5	$9.30	7.385%	$9.9868	$9.99	$10.00	$10.00
Purchase #6	$116.82	4.314%	$121.8596	$121.86	$121.85	$121.90
Purchase #7	$181.72	7.225%	$194.8493	$194.85	$194.85	$194.80
7 purchase totals =	$654.64		$706.4806	$706.48	$706.45	$706.50