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	$148.32	5.151%	$155.96	$155.96	$155.95	$156.00
Purchase #2	$101.93	6.382%	$108.4352	$108.44	$108.45	$108.40
Purchase #3	$90.98	10.105%	$100.1735	$100.17	$100.15	$100.20
Purchase #4	$213.55	12.149%	$239.4942	$239.49	$239.50	$239.50
Purchase #5	$71.53	10.211%	$78.8339	$78.83	$78.85	$78.80
Purchase #6	$190.68	11.374%	$212.3679	$212.37	$212.35	$212.40
Purchase #7	$121.88	5.371%	$128.4262	$128.43	$128.45	$128.40
7 purchase totals =	$938.87		$1,023.6909	$1,023.69	$1,023.70	$1,023.70