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	$93.95	13.231%	$106.3805	$106.38	$106.40	$106.40
Purchase #2	$123.64	6.721%	$131.9498	$131.95	$131.95	$131.90
Purchase #3	$76.52	5.725%	$80.9008	$80.90	$80.90	$80.90
Purchase #4	$90.97	5.727%	$96.1799	$96.18	$96.20	$96.20
Purchase #5	$43.26	8.113%	$46.7697	$46.77	$46.75	$46.80
Purchase #6	$40.54	10.264%	$44.701	$44.70	$44.70	$44.70
Purchase #7	$99.27	12.156%	$111.3373	$111.34	$111.35	$111.30
7 purchase totals =	$568.15		$618.2190	$618.22	$618.25	$618.20