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	$122.38	3.659%	$126.8579	$126.86	$126.85	$126.90
Purchase #2	$109.80	4.202%	$114.4138	$114.41	$114.40	$114.40
Purchase #3	$148.98	9.130%	$162.5819	$162.58	$162.60	$162.60
Purchase #4	$48.88	5.339%	$51.4897	$51.49	$51.50	$51.50
Purchase #5	$19.74	5.713%	$20.8677	$20.87	$20.85	$20.90
Purchase #6	$9.67	6.159%	$10.2656	$10.27	$10.25	$10.30
Purchase #7	$136.80	3.167%	$141.1325	$141.13	$141.15	$141.10
7 purchase totals =	$596.25		$627.6091	$627.61	$627.60	$627.70