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	$206.51	7.580%	$222.1635	$222.16	$222.15	$222.20
Purchase #2	$93.47	4.704%	$97.8668	$97.87	$97.85	$97.90
Purchase #3	$233.73	9.353%	$255.5908	$255.59	$255.60	$255.60
Purchase #4	$64.47	8.466%	$69.928	$69.93	$69.95	$69.90
Purchase #5	$200.82	11.478%	$223.8701	$223.87	$223.85	$223.90
Purchase #6	$226.38	6.676%	$241.4931	$241.49	$241.50	$241.50
Purchase #7	$173.88	7.269%	$186.5193	$186.52	$186.50	$186.50
7 purchase totals =	$1,199.26		$1,297.4316	$1,297.43	$1,297.40	$1,297.50