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	$68.89	13.184%	$77.9725	$77.97	$77.95	$78.00
Purchase #2	$118.33	6.273%	$125.7528	$125.75	$125.75	$125.80
Purchase #3	$163.71	5.806%	$173.215	$173.22	$173.20	$173.20
Purchase #4	$230.25	13.852%	$262.1442	$262.14	$262.15	$262.10
Purchase #5	$230.85	7.598%	$248.39	$248.39	$248.40	$248.40
Purchase #6	$92.86	8.161%	$100.4383	$100.44	$100.45	$100.40
Purchase #7	$40.92	3.677%	$42.4246	$42.42	$42.40	$42.40
7 purchase totals =	$945.81		$1,030.3374	$1,030.33	$1,030.30	$1,030.30