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	$153.80	7.272%	$164.9843	$164.98	$165.00	$165.00
Purchase #2	$56.88	4.777%	$59.5972	$59.60	$59.60	$59.60
Purchase #3	$92.42	7.232%	$99.1038	$99.10	$99.10	$99.10
Purchase #4	$230.60	10.826%	$255.5648	$255.56	$255.55	$255.60
Purchase #5	$160.79	4.683%	$168.3198	$168.32	$168.30	$168.30
Purchase #6	$130.83	9.693%	$143.5114	$143.51	$143.50	$143.50
Purchase #7	$143.64	4.739%	$150.4471	$150.45	$150.45	$150.40
7 purchase totals =	$968.96		$1,041.5284	$1,041.52	$1,041.50	$1,041.50