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	$170.61	3.641%	$176.8219	$176.82	$176.80	$176.80
Purchase #2	$108.96	10.127%	$119.9944	$119.99	$120.00	$120.00
Purchase #3	$153.64	12.370%	$172.6453	$172.65	$172.65	$172.60
Purchase #4	$108.87	7.227%	$116.738	$116.74	$116.75	$116.70
Purchase #5	$24.70	3.238%	$25.4998	$25.50	$25.50	$25.50
Purchase #6	$212.65	13.478%	$241.311	$241.31	$241.30	$241.30
Purchase #7	$206.47	7.801%	$222.5767	$222.58	$222.60	$222.60
7 purchase totals =	$985.90		$1,075.5871	$1,075.59	$1,075.60	$1,075.50