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	$24.45	5.423%	$25.7759	$25.78	$25.80	$25.80
Purchase #2	$106.71	4.798%	$111.8299	$111.83	$111.85	$111.80
Purchase #3	$19.37	7.620%	$20.846	$20.85	$20.85	$20.80
Purchase #4	$142.39	11.459%	$158.7065	$158.71	$158.70	$158.70
Purchase #5	$113.52	12.459%	$127.6635	$127.66	$127.65	$127.70
Purchase #6	$214.60	5.226%	$225.815	$225.82	$225.80	$225.80
Purchase #7	$111.33	10.797%	$123.3503	$123.35	$123.35	$123.40
7 purchase totals =	$732.37		$793.9871	$794.00	$794.00	$794.00