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	$240.26	9.411%	$262.8709	$262.87	$262.85	$262.90
Purchase #2	$21.64	11.543%	$24.1379	$24.14	$24.15	$24.10
Purchase #3	$232.78	10.284%	$256.7191	$256.72	$256.70	$256.70
Purchase #4	$129.45	12.340%	$145.4241	$145.42	$145.40	$145.40
Purchase #5	$115.64	6.393%	$123.0329	$123.03	$123.05	$123.00
Purchase #6	$63.84	12.106%	$71.5685	$71.57	$71.55	$71.60
Purchase #7	$168.99	7.265%	$181.2671	$181.27	$181.25	$181.30
7 purchase totals =	$972.60		$1,065.0205	$1,065.02	$1,064.95	$1,065.00