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	$78.75	5.463%	$83.0521	$83.05	$83.05	$83.10
Purchase #2	$94.33	11.127%	$104.8261	$104.83	$104.85	$104.80
Purchase #3	$145.76	5.789%	$154.198	$154.20	$154.20	$154.20
Purchase #4	$48.50	9.449%	$53.0828	$53.08	$53.10	$53.10
Purchase #5	$147.30	5.721%	$155.727	$155.73	$155.75	$155.70
Purchase #6	$92.86	7.116%	$99.4679	$99.47	$99.45	$99.50
Purchase #7	$231.35	10.426%	$255.4706	$255.47	$255.45	$255.50
7 purchase totals =	$838.85		$905.8245	$905.83	$905.85	$905.90