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	$138.27	12.729%	$155.8704	$155.87	$155.85	$155.90
Purchase #2	$160.85	4.218%	$167.6347	$167.63	$167.65	$167.60
Purchase #3	$43.69	6.672%	$46.605	$46.61	$46.60	$46.60
Purchase #4	$11.45	11.121%	$12.7234	$12.72	$12.70	$12.70
Purchase #5	$30.30	10.706%	$33.5439	$33.54	$33.55	$33.50
Purchase #6	$66.78	10.726%	$73.9428	$73.94	$73.95	$73.90
Purchase #7	$29.92	7.210%	$32.0772	$32.08	$32.10	$32.10
7 purchase totals =	$481.26		$522.3974	$522.39	$522.40	$522.30