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	$44.50	9.615%	$48.7787	$48.78	$48.80	$48.80
Purchase #2	$156.40	10.291%	$172.4951	$172.50	$172.50	$172.50
Purchase #3	$40.44	3.505%	$41.8574	$41.86	$41.85	$41.90
Purchase #4	$71.79	12.406%	$80.6963	$80.70	$80.70	$80.70
Purchase #5	$240.33	10.192%	$264.8244	$264.82	$264.80	$264.80
Purchase #6	$246.63	3.413%	$255.0475	$255.05	$255.05	$255.00
Purchase #7	$205.99	11.867%	$230.4348	$230.43	$230.45	$230.40
7 purchase totals =	$1,006.08		$1,094.1342	$1,094.14	$1,094.15	$1,094.10