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	$134.54	11.873%	$150.5139	$150.51	$150.50	$150.50
Purchase #2	$54.89	4.185%	$57.1871	$57.19	$57.20	$57.20
Purchase #3	$28.75	8.161%	$31.0963	$31.10	$31.10	$31.10
Purchase #4	$246.80	10.549%	$272.8349	$272.83	$272.85	$272.80
Purchase #5	$66.26	7.845%	$71.4581	$71.46	$71.45	$71.50
Purchase #6	$176.51	11.150%	$196.1909	$196.19	$196.20	$196.20
Purchase #7	$109.87	4.635%	$114.9625	$114.96	$114.95	$115.00
7 purchase totals =	$817.62		$894.2437	$894.24	$894.25	$894.30