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	$82.64	4.381%	$86.2605	$86.26	$86.25	$86.30
Purchase #2	$48.35	5.632%	$51.0731	$51.07	$51.05	$51.10
Purchase #3	$62.56	6.350%	$66.5326	$66.53	$66.55	$66.50
Purchase #4	$211.46	12.740%	$238.4	$238.40	$238.40	$238.40
Purchase #5	$153.55	4.211%	$160.016	$160.02	$160.00	$160.00
Purchase #6	$77.35	10.831%	$85.7278	$85.73	$85.75	$85.70
Purchase #7	$79.97	8.287%	$86.5971	$86.60	$86.60	$86.60
7 purchase totals =	$715.88		$774.6071	$774.61	$774.60	$774.60