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	$28.59	12.831%	$32.2584	$32.26	$32.25	$32.30
Purchase #2	$151.45	4.223%	$157.8457	$157.85	$157.85	$157.80
Purchase #3	$23.95	4.841%	$25.1094	$25.11	$25.10	$25.10
Purchase #4	$12.46	9.124%	$13.5969	$13.60	$13.60	$13.60
Purchase #5	$149.95	9.781%	$164.6166	$164.62	$164.60	$164.60
Purchase #6	$95.26	5.576%	$100.5717	$100.57	$100.55	$100.60
Purchase #7	$62.77	12.403%	$70.5554	$70.56	$70.55	$70.60
7 purchase totals =	$524.43		$564.5541	$564.57	$564.50	$564.60