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	$26.47	13.143%	$29.949	$29.95	$29.95	$29.90
Purchase #2	$104.39	8.162%	$112.9103	$112.91	$112.90	$112.90
Purchase #3	$9.47	9.841%	$10.4019	$10.40	$10.40	$10.40
Purchase #4	$30.70	9.233%	$33.5345	$33.53	$33.55	$33.50
Purchase #5	$155.34	10.326%	$171.3804	$171.38	$171.40	$171.40
Purchase #6	$65.92	10.553%	$72.8765	$72.88	$72.90	$72.90
Purchase #7	$61.98	6.168%	$65.8029	$65.80	$65.80	$65.80
7 purchase totals =	$454.27		$496.8555	$496.85	$496.90	$496.80