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	$163.93	7.731%	$176.6034	$176.60	$176.60	$176.60
Purchase #2	$80.43	12.504%	$90.487	$90.49	$90.50	$90.50
Purchase #3	$87.35	5.460%	$92.1193	$92.12	$92.10	$92.10
Purchase #4	$237.37	7.491%	$255.1514	$255.15	$255.15	$255.20
Purchase #5	$95.78	3.476%	$99.1093	$99.11	$99.10	$99.10
Purchase #6	$72.64	11.706%	$81.1432	$81.14	$81.15	$81.10
Purchase #7	$115.90	3.200%	$119.6088	$119.61	$119.60	$119.60
7 purchase totals =	$853.40		$914.2224	$914.22	$914.20	$914.20