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	$105.88	5.208%	$111.3942	$111.39	$111.40	$111.40
Purchase #2	$137.41	6.595%	$146.4722	$146.47	$146.45	$146.50
Purchase #3	$163.45	7.729%	$176.0831	$176.08	$176.10	$176.10
Purchase #4	$46.34	9.461%	$50.7242	$50.72	$50.70	$50.70
Purchase #5	$116.55	12.210%	$130.7808	$130.78	$130.80	$130.80
Purchase #6	$45.72	5.279%	$48.1336	$48.13	$48.15	$48.10
Purchase #7	$92.90	12.554%	$104.5627	$104.56	$104.55	$104.60
7 purchase totals =	$708.25		$768.1508	$768.13	$768.15	$768.20