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	$99.54	7.668%	$107.1727	$107.17	$107.15	$107.20
Purchase #2	$60.52	10.513%	$66.8825	$66.88	$66.90	$66.90
Purchase #3	$158.78	6.396%	$168.9356	$168.94	$168.95	$168.90
Purchase #4	$237.39	7.609%	$255.453	$255.45	$255.45	$255.50
Purchase #5	$159.81	11.622%	$178.3831	$178.38	$178.40	$178.40
Purchase #6	$221.91	6.801%	$237.0021	$237.00	$237.00	$237.00
Purchase #7	$144.95	5.232%	$152.5338	$152.53	$152.55	$152.50
7 purchase totals =	$1,082.90		$1,166.3628	$1,166.35	$1,166.40	$1,166.40