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	$127.99	11.430%	$142.6193	$142.62	$142.60	$142.60
Purchase #2	$229.70	10.369%	$253.5176	$253.52	$253.50	$253.50
Purchase #3	$158.47	3.429%	$163.9039	$163.90	$163.90	$163.90
Purchase #4	$56.29	11.376%	$62.6936	$62.69	$62.70	$62.70
Purchase #5	$34.85	9.368%	$38.1147	$38.11	$38.10	$38.10
Purchase #6	$56.80	8.841%	$61.8217	$61.82	$61.80	$61.80
Purchase #7	$31.54	4.424%	$32.9353	$32.94	$32.95	$32.90
7 purchase totals =	$695.64		$755.6061	$755.60	$755.55	$755.50