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	$169.64	5.132%	$178.3459	$178.35	$178.35	$178.30
Purchase #2	$69.47	12.613%	$78.2323	$78.23	$78.25	$78.20
Purchase #3	$80.55	8.326%	$87.2566	$87.26	$87.25	$87.30
Purchase #4	$45.70	11.291%	$50.86	$50.86	$50.85	$50.90
Purchase #5	$99.43	9.249%	$108.6263	$108.63	$108.65	$108.60
Purchase #6	$41.76	8.124%	$45.1526	$45.15	$45.15	$45.20
Purchase #7	$51.43	13.620%	$58.4348	$58.43	$58.45	$58.40
7 purchase totals =	$557.98		$606.9085	$606.91	$606.95	$606.90