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	$142.60	6.555%	$151.9474	$151.95	$151.95	$151.90
Purchase #2	$185.86	12.218%	$208.5684	$208.57	$208.55	$208.60
Purchase #3	$211.29	4.353%	$220.4875	$220.49	$220.50	$220.50
Purchase #4	$45.84	6.450%	$48.7967	$48.80	$48.80	$48.80
Purchase #5	$235.97	10.798%	$261.45	$261.45	$261.45	$261.50
Purchase #6	$214.47	8.783%	$233.3069	$233.31	$233.30	$233.30
Purchase #7	$49.69	11.388%	$55.3487	$55.35	$55.35	$55.30
7 purchase totals =	$1,085.72		$1,179.9056	$1,179.92	$1,179.90	$1,179.90