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	$116.41	7.230%	$124.8264	$124.83	$124.85	$124.80
Purchase #2	$241.82	5.470%	$255.0476	$255.05	$255.05	$255.00
Purchase #3	$153.53	4.438%	$160.3437	$160.34	$160.35	$160.30
Purchase #4	$165.75	3.708%	$171.896	$171.90	$171.90	$171.90
Purchase #5	$205.85	5.296%	$216.7518	$216.75	$216.75	$216.80
Purchase #6	$23.58	8.291%	$25.535	$25.54	$25.55	$25.50
Purchase #7	$57.82	12.824%	$65.2348	$65.23	$65.25	$65.20
7 purchase totals =	$964.76		$1,019.6353	$1,019.64	$1,019.70	$1,019.50