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	$218.84	5.307%	$230.4538	$230.45	$230.45	$230.50
Purchase #2	$171.28	12.360%	$192.4502	$192.45	$192.45	$192.50
Purchase #3	$196.83	8.563%	$213.6846	$213.68	$213.70	$213.70
Purchase #4	$125.78	5.208%	$132.3306	$132.33	$132.35	$132.30
Purchase #5	$73.51	11.858%	$82.2268	$82.23	$82.25	$82.20
Purchase #6	$99.30	9.283%	$108.518	$108.52	$108.50	$108.50
Purchase #7	$150.88	3.800%	$156.6134	$156.61	$156.60	$156.60
7 purchase totals =	$1,036.42		$1,116.2774	$1,116.27	$1,116.30	$1,116.30