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	$161.68	9.630%	$177.2498	$177.25	$177.25	$177.20
Purchase #2	$74.27	3.138%	$76.6006	$76.60	$76.60	$76.60
Purchase #3	$212.98	4.449%	$222.4555	$222.46	$222.45	$222.50
Purchase #4	$37.75	10.848%	$41.8451	$41.85	$41.85	$41.80
Purchase #5	$229.75	11.215%	$255.5165	$255.52	$255.50	$255.50
Purchase #6	$89.97	10.107%	$99.0633	$99.06	$99.05	$99.10
Purchase #7	$148.60	4.408%	$155.1503	$155.15	$155.15	$155.20
7 purchase totals =	$955.00		$1,027.8811	$1,027.89	$1,027.85	$1,027.90