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	$90.69	4.180%	$94.4808	$94.48	$94.50	$94.50
Purchase #2	$125.25	13.401%	$142.0348	$142.03	$142.05	$142.00
Purchase #3	$139.38	3.727%	$144.5747	$144.57	$144.55	$144.60
Purchase #4	$225.49	12.390%	$253.4282	$253.43	$253.45	$253.40
Purchase #5	$20.56	7.558%	$22.1139	$22.11	$22.10	$22.10
Purchase #6	$242.98	11.778%	$271.5982	$271.60	$271.60	$271.60
Purchase #7	$228.58	11.809%	$255.573	$255.57	$255.55	$255.60
7 purchase totals =	$1,072.93		$1,183.8036	$1,183.79	$1,183.80	$1,183.80