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	$92.83	8.318%	$100.5516	$100.55	$100.55	$100.60
Purchase #2	$31.32	9.350%	$34.2484	$34.25	$34.25	$34.20
Purchase #3	$41.67	4.696%	$43.6268	$43.63	$43.65	$43.60
Purchase #4	$83.59	8.470%	$90.6701	$90.67	$90.65	$90.70
Purchase #5	$176.47	7.183%	$189.1458	$189.15	$189.15	$189.10
Purchase #6	$102.86	12.594%	$115.8142	$115.81	$115.80	$115.80
Purchase #7	$115.84	6.509%	$123.38	$123.38	$123.40	$123.40
7 purchase totals =	$644.58		$697.4369	$697.44	$697.45	$697.40