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	$63.64	6.342%	$67.676	$67.68	$67.70	$67.70
Purchase #2	$212.76	4.114%	$221.5129	$221.51	$221.50	$221.50
Purchase #3	$68.82	13.832%	$78.3392	$78.34	$78.35	$78.30
Purchase #4	$103.77	12.602%	$116.8471	$116.85	$116.85	$116.80
Purchase #5	$231.39	10.193%	$254.9756	$254.98	$255.00	$255.00
Purchase #6	$242.52	9.243%	$264.9361	$264.94	$264.95	$264.90
Purchase #7	$86.34	9.706%	$94.7202	$94.72	$94.70	$94.70
7 purchase totals =	$1,009.24		$1,099.0071	$1,099.02	$1,099.05	$1,098.90