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	$105.25	9.760%	$115.5224	$115.52	$115.50	$115.50
Purchase #2	$15.80	10.307%	$17.4285	$17.43	$17.45	$17.40
Purchase #3	$131.42	10.264%	$144.9089	$144.91	$144.90	$144.90
Purchase #4	$10.51	13.742%	$11.9543	$11.95	$11.95	$12.00
Purchase #5	$46.96	3.293%	$48.5064	$48.51	$48.50	$48.50
Purchase #6	$87.45	13.520%	$99.2732	$99.27	$99.25	$99.30
Purchase #7	$246.29	13.104%	$278.5638	$278.56	$278.55	$278.60
7 purchase totals =	$643.68		$716.1575	$716.15	$716.10	$716.20