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	$98.86	10.472%	$109.2126	$109.21	$109.20	$109.20
Purchase #2	$104.32	13.224%	$118.1153	$118.12	$118.10	$118.10
Purchase #3	$51.57	6.540%	$54.9427	$54.94	$54.95	$54.90
Purchase #4	$134.94	3.117%	$139.1461	$139.15	$139.15	$139.10
Purchase #5	$57.37	9.732%	$62.9532	$62.95	$62.95	$63.00
Purchase #6	$108.44	7.770%	$116.8658	$116.87	$116.85	$116.90
Purchase #7	$20.75	9.162%	$22.6511	$22.65	$22.65	$22.70
7 purchase totals =	$576.25		$623.8868	$623.89	$623.85	$623.90