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	$235.62	5.525%	$248.638	$248.64	$248.65	$248.60
Purchase #2	$112.66	13.259%	$127.5976	$127.60	$127.60	$127.60
Purchase #3	$182.64	9.777%	$200.4967	$200.50	$200.50	$200.50
Purchase #4	$65.28	10.320%	$72.0169	$72.02	$72.00	$72.00
Purchase #5	$64.81	12.145%	$72.6812	$72.68	$72.70	$72.70
Purchase #6	$118.86	10.453%	$131.2844	$131.28	$131.30	$131.30
Purchase #7	$96.92	8.692%	$105.3443	$105.34	$105.35	$105.30
7 purchase totals =	$876.79		$958.0591	$958.06	$958.10	$958.00