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	$183.85	12.685%	$207.1714	$207.17	$207.15	$207.20
Purchase #2	$108.98	7.195%	$116.8211	$116.82	$116.80	$116.80
Purchase #3	$103.32	5.759%	$109.2702	$109.27	$109.25	$109.30
Purchase #4	$145.78	3.443%	$150.7992	$150.80	$150.80	$150.80
Purchase #5	$42.30	4.389%	$44.1565	$44.16	$44.15	$44.20
Purchase #6	$25.62	13.567%	$29.0959	$29.10	$29.10	$29.10
Purchase #7	$94.39	10.131%	$103.9527	$103.95	$103.95	$104.00
7 purchase totals =	$704.24		$761.2670	$761.27	$761.20	$761.40