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	$205.62	4.523%	$214.9202	$214.92	$214.90	$214.90
Purchase #2	$138.59	3.854%	$143.9313	$143.93	$143.95	$143.90
Purchase #3	$131.65	3.760%	$136.6	$136.60	$136.60	$136.60
Purchase #4	$178.80	3.844%	$185.6731	$185.67	$185.65	$185.70
Purchase #5	$190.95	9.210%	$208.5365	$208.54	$208.55	$208.50
Purchase #6	$158.53	13.326%	$179.6557	$179.66	$179.65	$179.70
Purchase #7	$68.58	5.107%	$72.0824	$72.08	$72.10	$72.10
7 purchase totals =	$1,072.72		$1,141.3992	$1,141.40	$1,141.40	$1,141.40