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	$214.90	6.838%	$229.5949	$229.59	$229.60	$229.60
Purchase #2	$143.75	4.639%	$150.4186	$150.42	$150.40	$150.40
Purchase #3	$152.42	10.656%	$168.6619	$168.66	$168.65	$168.70
Purchase #4	$132.25	9.531%	$144.8547	$144.85	$144.85	$144.90
Purchase #5	$46.37	4.322%	$48.3741	$48.37	$48.35	$48.40
Purchase #6	$228.74	6.352%	$243.2696	$243.27	$243.25	$243.30
Purchase #7	$211.32	5.239%	$222.3911	$222.39	$222.40	$222.40
7 purchase totals =	$1,129.75		$1,207.5649	$1,207.55	$1,207.50	$1,207.70