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	$214.48	4.842%	$224.8651	$224.87	$224.85	$224.90
Purchase #2	$118.66	10.603%	$131.2415	$131.24	$131.25	$131.20
Purchase #3	$84.87	6.209%	$90.1396	$90.14	$90.15	$90.10
Purchase #4	$190.45	9.307%	$208.1752	$208.18	$208.20	$208.20
Purchase #5	$241.70	7.157%	$258.9985	$259.00	$259.00	$259.00
Purchase #6	$196.31	13.351%	$222.5193	$222.52	$222.50	$222.50
Purchase #7	$203.75	11.639%	$227.4645	$227.46	$227.45	$227.50
7 purchase totals =	$1,250.22		$1,363.4037	$1,363.41	$1,363.40	$1,363.40