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	$242.64	10.778%	$268.7917	$268.79	$268.80	$268.80
Purchase #2	$18.79	10.453%	$20.7541	$20.75	$20.75	$20.80
Purchase #3	$43.85	6.246%	$46.5889	$46.59	$46.60	$46.60
Purchase #4	$67.70	12.739%	$76.3243	$76.32	$76.30	$76.30
Purchase #5	$148.56	3.382%	$153.5843	$153.58	$153.60	$153.60
Purchase #6	$55.40	12.398%	$62.2685	$62.27	$62.25	$62.30
Purchase #7	$132.47	5.390%	$139.6101	$139.61	$139.60	$139.60
7 purchase totals =	$709.41		$767.9219	$767.91	$767.90	$768.00