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	$168.94	8.330%	$183.0127	$183.01	$183.00	$183.00
Purchase #2	$44.28	4.758%	$46.3868	$46.39	$46.40	$46.40
Purchase #3	$95.62	10.726%	$105.8762	$105.88	$105.90	$105.90
Purchase #4	$139.80	9.550%	$153.1509	$153.15	$153.15	$153.20
Purchase #5	$91.54	9.353%	$100.1017	$100.10	$100.10	$100.10
Purchase #6	$16.42	12.549%	$18.4805	$18.48	$18.50	$18.50
Purchase #7	$72.98	11.298%	$81.2253	$81.23	$81.25	$81.20
7 purchase totals =	$629.58		$688.2341	$688.24	$688.30	$688.30