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	$72.46	7.208%	$77.6829	$77.68	$77.70	$77.70
Purchase #2	$52.86	13.870%	$60.1917	$60.19	$60.20	$60.20
Purchase #3	$185.29	3.395%	$191.5806	$191.58	$191.60	$191.60
Purchase #4	$44.46	13.116%	$50.2914	$50.29	$50.30	$50.30
Purchase #5	$10.73	10.805%	$11.8894	$11.89	$11.90	$11.90
Purchase #6	$38.86	8.449%	$42.1433	$42.14	$42.15	$42.10
Purchase #7	$7.81	7.153%	$8.3686	$8.37	$8.35	$8.40
7 purchase totals =	$412.47		$442.1479	$442.14	$442.20	$442.20