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	$163.71	6.246%	$173.9353	$173.94	$173.95	$173.90
Purchase #2	$126.66	12.398%	$142.3633	$142.36	$142.35	$142.40
Purchase #3	$111.67	11.492%	$124.5031	$124.50	$124.50	$124.50
Purchase #4	$18.39	3.202%	$18.9788	$18.98	$19.00	$19.00
Purchase #5	$157.46	7.514%	$169.2915	$169.29	$169.30	$169.30
Purchase #6	$19.50	8.392%	$21.1364	$21.14	$21.15	$21.10
Purchase #7	$72.59	13.517%	$82.402	$82.40	$82.40	$82.40
7 purchase totals =	$669.98		$732.6104	$732.61	$732.65	$732.60