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	$53.69	12.226%	$60.2541	$60.25	$60.25	$60.30
Purchase #2	$133.59	13.763%	$151.976	$151.98	$152.00	$152.00
Purchase #3	$222.75	4.845%	$233.5422	$233.54	$233.55	$233.50
Purchase #4	$22.45	3.620%	$23.2627	$23.26	$23.25	$23.30
Purchase #5	$89.79	13.407%	$101.8281	$101.83	$101.85	$101.80
Purchase #6	$74.73	9.803%	$82.0558	$82.06	$82.05	$82.10
Purchase #7	$208.87	9.381%	$228.4641	$228.46	$228.45	$228.50
7 purchase totals =	$805.87		$881.3830	$881.38	$881.40	$881.50