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	$232.34	10.602%	$256.9727	$256.97	$256.95	$257.00
Purchase #2	$233.75	4.197%	$243.5605	$243.56	$243.55	$243.60
Purchase #3	$231.53	10.160%	$255.0534	$255.05	$255.05	$255.10
Purchase #4	$72.46	8.244%	$78.4336	$78.43	$78.45	$78.40
Purchase #5	$22.76	10.545%	$25.16	$25.16	$25.15	$25.20
Purchase #6	$65.94	12.869%	$74.4258	$74.43	$74.45	$74.40
Purchase #7	$112.85	12.769%	$127.2598	$127.26	$127.25	$127.30
7 purchase totals =	$971.63		$1,060.8658	$1,060.86	$1,060.85	$1,061.00