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	$209.70	13.651%	$238.3261	$238.33	$238.35	$238.30
Purchase #2	$55.76	10.465%	$61.5953	$61.60	$61.60	$61.60
Purchase #3	$20.45	6.555%	$21.7905	$21.79	$21.80	$21.80
Purchase #4	$98.65	9.485%	$108.007	$108.01	$108.00	$108.00
Purchase #5	$132.33	9.614%	$145.0522	$145.05	$145.05	$145.10
Purchase #6	$143.45	4.810%	$150.3499	$150.35	$150.35	$150.30
Purchase #7	$6.76	9.247%	$7.3851	$7.39	$7.40	$7.40
7 purchase totals =	$667.10		$732.5061	$732.52	$732.55	$732.50