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	$139.85	9.144%	$152.6379	$152.64	$152.65	$152.60
Purchase #2	$121.29	7.521%	$130.4122	$130.41	$130.40	$130.40
Purchase #3	$103.37	7.378%	$110.9966	$111.00	$111.00	$111.00
Purchase #4	$224.55	5.824%	$237.6278	$237.63	$237.65	$237.60
Purchase #5	$131.74	8.622%	$143.0986	$143.10	$143.10	$143.10
Purchase #6	$59.38	6.579%	$63.2866	$63.29	$63.30	$63.30
Purchase #7	$16.71	12.845%	$18.8564	$18.86	$18.85	$18.90
7 purchase totals =	$796.89		$856.9161	$856.93	$856.95	$856.90