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	$219.61	10.106%	$241.8038	$241.80	$241.80	$241.80
Purchase #2	$113.83	11.727%	$127.1788	$127.18	$127.20	$127.20
Purchase #3	$164.41	5.592%	$173.6038	$173.60	$173.60	$173.60
Purchase #4	$59.75	7.130%	$64.0102	$64.01	$64.00	$64.00
Purchase #5	$88.70	10.285%	$97.8228	$97.82	$97.80	$97.80
Purchase #6	$120.87	11.242%	$134.4582	$134.46	$134.45	$134.50
Purchase #7	$233.51	9.209%	$255.0139	$255.01	$255.00	$255.00
7 purchase totals =	$1,000.68		$1,093.8915	$1,093.88	$1,093.85	$1,093.90