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	$169.29	5.415%	$178.4571	$178.46	$178.45	$178.50
Purchase #2	$229.94	5.386%	$242.3246	$242.32	$242.30	$242.30
Purchase #3	$85.84	11.728%	$95.9073	$95.91	$95.90	$95.90
Purchase #4	$132.58	5.766%	$140.2246	$140.22	$140.20	$140.20
Purchase #5	$177.28	4.194%	$184.7151	$184.72	$184.70	$184.70
Purchase #6	$29.62	13.361%	$33.5775	$33.58	$33.60	$33.60
Purchase #7	$134.80	6.205%	$143.1643	$143.16	$143.15	$143.20
7 purchase totals =	$959.35		$1,018.3705	$1,018.37	$1,018.30	$1,018.40