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	$150.77	11.383%	$167.9321	$167.93	$167.95	$167.90
Purchase #2	$146.58	11.383%	$163.2652	$163.27	$163.25	$163.30
Purchase #3	$199.66	11.501%	$222.6229	$222.62	$222.60	$222.60
Purchase #4	$40.79	5.806%	$43.1583	$43.16	$43.15	$43.20
Purchase #5	$125.51	9.535%	$137.4774	$137.48	$137.50	$137.50
Purchase #6	$238.56	10.117%	$262.6951	$262.70	$262.70	$262.70
Purchase #7	$65.95	3.711%	$68.3974	$68.40	$68.40	$68.40
7 purchase totals =	$967.82		$1,065.5484	$1,065.56	$1,065.55	$1,065.60