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	$60.25	8.128%	$65.1471	$65.15	$65.15	$65.10
Purchase #2	$38.75	5.441%	$40.8584	$40.86	$40.85	$40.90
Purchase #3	$18.43	5.655%	$19.4722	$19.47	$19.45	$19.50
Purchase #4	$48.86	5.734%	$51.6616	$51.66	$51.65	$51.70
Purchase #5	$79.44	9.851%	$87.2656	$87.27	$87.25	$87.30
Purchase #6	$11.88	3.720%	$12.3219	$12.32	$12.30	$12.30
Purchase #7	$156.94	7.570%	$168.8204	$168.82	$168.80	$168.80
7 purchase totals =	$414.55		$445.5472	$445.55	$445.45	$445.60