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	$154.32	12.387%	$173.4356	$173.44	$173.45	$173.40
Purchase #2	$109.41	13.109%	$123.7526	$123.75	$123.75	$123.80
Purchase #3	$233.41	9.648%	$255.9294	$255.93	$255.95	$255.90
Purchase #4	$128.74	11.205%	$143.1653	$143.17	$143.15	$143.20
Purchase #5	$151.38	4.197%	$157.7334	$157.73	$157.75	$157.70
Purchase #6	$138.81	5.189%	$146.0129	$146.01	$146.00	$146.00
Purchase #7	$64.36	11.873%	$72.0015	$72.00	$72.00	$72.00
7 purchase totals =	$980.43		$1,072.0307	$1,072.03	$1,072.05	$1,072.00