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	$167.60	12.682%	$188.855	$188.86	$188.85	$188.90
Purchase #2	$74.27	8.615%	$80.6684	$80.67	$80.65	$80.70
Purchase #3	$237.46	10.725%	$262.9276	$262.93	$262.95	$262.90
Purchase #4	$99.86	5.569%	$105.4212	$105.42	$105.40	$105.40
Purchase #5	$132.42	5.278%	$139.4091	$139.41	$139.40	$139.40
Purchase #6	$234.96	13.749%	$267.2647	$267.26	$267.25	$267.30
Purchase #7	$18.34	10.572%	$20.2789	$20.28	$20.30	$20.30
7 purchase totals =	$964.91		$1,064.8249	$1,064.83	$1,064.80	$1,064.90