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	$148.54	10.466%	$164.0862	$164.09	$164.10	$164.10
Purchase #2	$101.88	10.805%	$112.8881	$112.89	$112.90	$112.90
Purchase #3	$145.98	8.656%	$158.616	$158.62	$158.60	$158.60
Purchase #4	$205.93	9.368%	$225.2215	$225.22	$225.20	$225.20
Purchase #5	$58.64	6.731%	$62.5871	$62.59	$62.60	$62.60
Purchase #6	$76.38	4.514%	$79.8278	$79.83	$79.85	$79.80
Purchase #7	$60.27	7.817%	$64.9813	$64.98	$65.00	$65.00
7 purchase totals =	$797.62		$868.2080	$868.22	$868.25	$868.20