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	$225.91	10.484%	$249.5944	$249.59	$249.60	$249.60
Purchase #2	$64.67	10.836%	$71.6776	$71.68	$71.70	$71.70
Purchase #3	$241.93	10.840%	$268.1552	$268.16	$268.15	$268.20
Purchase #4	$230.56	5.254%	$242.6736	$242.67	$242.65	$242.70
Purchase #5	$41.99	11.144%	$46.6694	$46.67	$46.65	$46.70
Purchase #6	$76.41	8.697%	$83.0554	$83.06	$83.05	$83.10
Purchase #7	$52.37	9.838%	$57.5222	$57.52	$57.50	$57.50
7 purchase totals =	$933.84		$1,019.3478	$1,019.35	$1,019.30	$1,019.50