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	$147.78	4.212%	$154.0045	$154.00	$154.00	$154.00
Purchase #2	$222.79	13.727%	$253.3724	$253.37	$253.35	$253.40
Purchase #3	$156.35	4.149%	$162.837	$162.84	$162.85	$162.80
Purchase #4	$143.64	3.181%	$148.2092	$148.21	$148.20	$148.20
Purchase #5	$103.52	7.861%	$111.6577	$111.66	$111.65	$111.70
Purchase #6	$59.64	10.723%	$66.0352	$66.04	$66.05	$66.00
Purchase #7	$174.66	9.145%	$190.6327	$190.63	$190.65	$190.60
7 purchase totals =	$1,008.38		$1,086.7487	$1,086.75	$1,086.75	$1,086.70