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	$217.80	7.587%	$234.3245	$234.32	$234.30	$234.30
Purchase #2	$72.89	12.508%	$82.0071	$82.01	$82.00	$82.00
Purchase #3	$11.77	10.313%	$12.9838	$12.98	$13.00	$13.00
Purchase #4	$239.96	6.320%	$255.1255	$255.13	$255.15	$255.10
Purchase #5	$28.79	11.559%	$32.1178	$32.12	$32.10	$32.10
Purchase #6	$64.83	6.718%	$69.1853	$69.19	$69.20	$69.20
Purchase #7	$74.48	5.668%	$78.7015	$78.70	$78.70	$78.70
7 purchase totals =	$710.52		$764.4455	$764.45	$764.45	$764.40