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	$158.58	6.484%	$168.8623	$168.86	$168.85	$168.90
Purchase #2	$236.92	7.174%	$253.9166	$253.92	$253.90	$253.90
Purchase #3	$129.94	5.188%	$136.6813	$136.68	$136.70	$136.70
Purchase #4	$153.96	12.735%	$173.5668	$173.57	$173.55	$173.60
Purchase #5	$157.45	12.141%	$176.566	$176.57	$176.55	$176.60
Purchase #6	$151.26	3.372%	$156.3605	$156.36	$156.35	$156.40
Purchase #7	$83.66	7.501%	$89.9353	$89.94	$89.95	$89.90
7 purchase totals =	$1,071.77		$1,155.8888	$1,155.90	$1,155.85	$1,156.00