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	$33.62	13.566%	$38.1809	$38.18	$38.20	$38.20
Purchase #2	$70.33	3.388%	$72.7128	$72.71	$72.70	$72.70
Purchase #3	$80.66	12.737%	$90.9337	$90.93	$90.95	$90.90
Purchase #4	$63.25	9.748%	$69.4156	$69.42	$69.40	$69.40
Purchase #5	$100.31	9.183%	$109.5215	$109.52	$109.50	$109.50
Purchase #6	$132.87	3.191%	$137.1099	$137.11	$137.10	$137.10
Purchase #7	$238.60	7.758%	$257.1106	$257.11	$257.10	$257.10
7 purchase totals =	$719.64		$774.9850	$774.98	$774.95	$774.90