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	$38.52	13.554%	$43.741	$43.74	$43.75	$43.70
Purchase #2	$30.46	13.133%	$34.4603	$34.46	$34.45	$34.50
Purchase #3	$19.95	7.625%	$21.4712	$21.47	$21.45	$21.50
Purchase #4	$240.54	6.721%	$256.7067	$256.71	$256.70	$256.70
Purchase #5	$203.39	11.826%	$227.4429	$227.44	$227.45	$227.40
Purchase #6	$19.73	4.133%	$20.5454	$20.55	$20.55	$20.50
Purchase #7	$70.97	7.685%	$76.424	$76.42	$76.40	$76.40
7 purchase totals =	$623.56		$680.7915	$680.79	$680.75	$680.70