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	$211.83	11.589%	$236.379	$236.38	$236.40	$236.40
Purchase #2	$59.68	11.341%	$66.4483	$66.45	$66.45	$66.40
Purchase #3	$24.82	9.147%	$27.0903	$27.09	$27.10	$27.10
Purchase #4	$175.95	8.861%	$191.5409	$191.54	$191.55	$191.50
Purchase #5	$67.25	10.594%	$74.3745	$74.37	$74.35	$74.40
Purchase #6	$153.52	11.780%	$171.6047	$171.60	$171.60	$171.60
Purchase #7	$93.73	5.596%	$98.9751	$98.98	$99.00	$99.00
7 purchase totals =	$786.78		$866.4128	$866.41	$866.45	$866.40