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	$175.52	5.180%	$184.6119	$184.61	$184.60	$184.60
Purchase #2	$50.45	7.124%	$54.0441	$54.04	$54.05	$54.00
Purchase #3	$40.72	4.229%	$42.442	$42.44	$42.45	$42.40
Purchase #4	$30.95	8.711%	$33.6461	$33.65	$33.65	$33.60
Purchase #5	$164.30	7.155%	$176.0557	$176.06	$176.05	$176.10
Purchase #6	$139.81	13.502%	$158.6871	$158.69	$158.70	$158.70
Purchase #7	$19.90	13.491%	$22.5847	$22.58	$22.60	$22.60
7 purchase totals =	$621.65		$672.0716	$672.07	$672.10	$672.00