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	$56.87	9.516%	$62.2817	$62.28	$62.30	$62.30
Purchase #2	$226.85	3.361%	$234.4744	$234.47	$234.45	$234.50
Purchase #3	$79.90	12.345%	$89.7637	$89.76	$89.75	$89.80
Purchase #4	$172.76	13.559%	$196.1845	$196.18	$196.20	$196.20
Purchase #5	$52.98	11.529%	$59.0881	$59.09	$59.10	$59.10
Purchase #6	$8.75	6.548%	$9.323	$9.32	$9.30	$9.30
Purchase #7	$166.57	4.497%	$174.0607	$174.06	$174.05	$174.10
7 purchase totals =	$764.68		$825.1761	$825.16	$825.15	$825.30