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	$118.62	6.550%	$126.3896	$126.39	$126.40	$126.40
Purchase #2	$238.78	6.853%	$255.1436	$255.14	$255.15	$255.10
Purchase #3	$141.76	6.464%	$150.9234	$150.92	$150.90	$150.90
Purchase #4	$162.49	9.439%	$177.8274	$177.83	$177.85	$177.80
Purchase #5	$141.86	10.476%	$156.7213	$156.72	$156.70	$156.70
Purchase #6	$176.54	8.537%	$191.6112	$191.61	$191.60	$191.60
Purchase #7	$91.93	9.361%	$100.5356	$100.54	$100.55	$100.50
7 purchase totals =	$1,071.98		$1,159.1521	$1,159.15	$1,159.15	$1,159.00