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	$125.55	6.792%	$134.0774	$134.08	$134.10	$134.10
Purchase #2	$99.28	10.750%	$109.9526	$109.95	$109.95	$110.00
Purchase #3	$12.70	5.154%	$13.3546	$13.35	$13.35	$13.40
Purchase #4	$139.68	12.261%	$156.8062	$156.81	$156.80	$156.80
Purchase #5	$214.31	8.856%	$233.2893	$233.29	$233.30	$233.30
Purchase #6	$63.93	12.718%	$72.0606	$72.06	$72.05	$72.10
Purchase #7	$88.36	13.641%	$100.4132	$100.41	$100.40	$100.40
7 purchase totals =	$743.81		$819.9539	$819.95	$819.95	$820.10