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	$46.64	6.311%	$49.5835	$49.58	$49.60	$49.60
Purchase #2	$116.92	8.855%	$127.2733	$127.27	$127.25	$127.30
Purchase #3	$144.73	5.536%	$152.7423	$152.74	$152.75	$152.70
Purchase #4	$150.73	3.551%	$156.0824	$156.08	$156.10	$156.10
Purchase #5	$179.58	6.632%	$191.4897	$191.49	$191.50	$191.50
Purchase #6	$29.60	12.724%	$33.3663	$33.37	$33.35	$33.40
Purchase #7	$47.91	7.704%	$51.601	$51.60	$51.60	$51.60
7 purchase totals =	$716.11		$762.1385	$762.13	$762.15	$762.20