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	$219.46	10.667%	$242.8698	$242.87	$242.85	$242.90
Purchase #2	$161.90	13.722%	$184.1159	$184.12	$184.10	$184.10
Purchase #3	$140.44	5.750%	$148.5153	$148.52	$148.50	$148.50
Purchase #4	$80.82	10.597%	$89.3845	$89.38	$89.40	$89.40
Purchase #5	$52.99	4.262%	$55.2484	$55.25	$55.25	$55.20
Purchase #6	$151.60	9.189%	$165.5305	$165.53	$165.55	$165.50
Purchase #7	$212.27	5.652%	$224.2675	$224.27	$224.25	$224.30
7 purchase totals =	$1,019.48		$1,109.9319	$1,109.94	$1,109.90	$1,109.90