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	$18.56	4.345%	$19.3664	$19.37	$19.35	$19.40
Purchase #2	$16.32	12.642%	$18.3832	$18.38	$18.40	$18.40
Purchase #3	$52.58	13.105%	$59.4706	$59.47	$59.45	$59.50
Purchase #4	$79.68	9.529%	$87.2727	$87.27	$87.25	$87.30
Purchase #5	$241.52	4.754%	$253.0019	$253.00	$253.00	$253.00
Purchase #6	$133.96	7.595%	$144.1343	$144.13	$144.15	$144.10
Purchase #7	$10.30	11.617%	$11.4966	$11.50	$11.50	$11.50
7 purchase totals =	$552.92		$593.1257	$593.12	$593.10	$593.20