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	$228.51	5.301%	$240.6233	$240.62	$240.60	$240.60
Purchase #2	$100.69	11.438%	$112.2069	$112.21	$112.20	$112.20
Purchase #3	$222.97	13.772%	$253.6774	$253.68	$253.70	$253.70
Purchase #4	$133.28	5.774%	$140.9756	$140.98	$141.00	$141.00
Purchase #5	$228.88	11.553%	$255.3225	$255.32	$255.30	$255.30
Purchase #6	$86.70	9.835%	$95.2269	$95.23	$95.25	$95.20
Purchase #7	$70.40	4.385%	$73.487	$73.49	$73.50	$73.50
7 purchase totals =	$1,071.43		$1,171.5196	$1,171.53	$1,171.55	$1,171.50