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	$10.58	7.202%	$11.342	$11.34	$11.35	$11.30
Purchase #2	$54.36	9.632%	$59.596	$59.60	$59.60	$59.60
Purchase #3	$49.28	4.681%	$51.5868	$51.59	$51.60	$51.60
Purchase #4	$158.95	4.699%	$166.4191	$166.42	$166.40	$166.40
Purchase #5	$143.44	7.286%	$153.891	$153.89	$153.90	$153.90
Purchase #6	$140.78	3.289%	$145.4103	$145.41	$145.40	$145.40
Purchase #7	$79.53	13.504%	$90.2697	$90.27	$90.25	$90.30
7 purchase totals =	$636.92		$678.5149	$678.52	$678.50	$678.50