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	$148.70	6.763%	$158.7566	$158.76	$158.75	$158.80
Purchase #2	$129.98	8.768%	$141.3766	$141.38	$141.40	$141.40
Purchase #3	$10.99	6.317%	$11.6842	$11.68	$11.70	$11.70
Purchase #4	$61.86	9.651%	$67.8301	$67.83	$67.85	$67.80
Purchase #5	$133.51	9.316%	$145.9478	$145.95	$145.95	$145.90
Purchase #6	$75.95	12.238%	$85.2448	$85.24	$85.25	$85.20
Purchase #7	$39.35	10.470%	$43.4699	$43.47	$43.45	$43.50
7 purchase totals =	$600.34		$654.3100	$654.31	$654.35	$654.30