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	$203.32	9.493%	$222.6212	$222.62	$222.60	$222.60
Purchase #2	$139.81	4.147%	$145.6079	$145.61	$145.60	$145.60
Purchase #3	$167.74	11.287%	$186.6728	$186.67	$186.65	$186.70
Purchase #4	$73.94	3.367%	$76.4296	$76.43	$76.45	$76.40
Purchase #5	$107.87	3.732%	$111.8957	$111.90	$111.90	$111.90
Purchase #6	$155.79	7.843%	$168.0086	$168.01	$168.00	$168.00
Purchase #7	$37.75	13.716%	$42.9278	$42.93	$42.95	$42.90
7 purchase totals =	$886.22		$954.1636	$954.17	$954.15	$954.10