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	$29.98	8.508%	$32.5307	$32.53	$32.55	$32.50
Purchase #2	$11.77	10.172%	$12.9672	$12.97	$12.95	$13.00
Purchase #3	$223.55	11.149%	$248.4736	$248.47	$248.45	$248.50
Purchase #4	$110.71	7.582%	$119.104	$119.10	$119.10	$119.10
Purchase #5	$110.71	5.636%	$116.9496	$116.95	$116.95	$116.90
Purchase #6	$93.68	7.379%	$100.5926	$100.59	$100.60	$100.60
Purchase #7	$127.78	6.838%	$136.5176	$136.52	$136.50	$136.50
7 purchase totals =	$708.18		$767.1353	$767.13	$767.10	$767.10