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	$123.70	6.746%	$132.0448	$132.04	$132.05	$132.00
Purchase #2	$155.99	11.224%	$173.4983	$173.50	$173.50	$173.50
Purchase #3	$237.48	13.321%	$269.1147	$269.11	$269.10	$269.10
Purchase #4	$250.45	9.111%	$273.2685	$273.27	$273.25	$273.30
Purchase #5	$82.77	13.612%	$94.0367	$94.04	$94.05	$94.00
Purchase #6	$142.93	10.128%	$157.406	$157.41	$157.40	$157.40
Purchase #7	$114.39	7.741%	$123.2449	$123.24	$123.25	$123.20
7 purchase totals =	$1,107.71		$1,222.6139	$1,222.61	$1,222.60	$1,222.50