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	$172.56	8.452%	$187.1448	$187.14	$187.15	$187.10
Purchase #2	$61.53	11.328%	$68.5001	$68.50	$68.50	$68.50
Purchase #3	$239.63	6.256%	$254.6213	$254.62	$254.60	$254.60
Purchase #4	$121.85	4.609%	$127.4661	$127.47	$127.45	$127.50
Purchase #5	$44.42	10.608%	$49.1321	$49.13	$49.15	$49.10
Purchase #6	$108.83	5.565%	$114.8864	$114.89	$114.90	$114.90
Purchase #7	$244.67	11.771%	$273.4701	$273.47	$273.45	$273.50
7 purchase totals =	$993.49		$1,075.2209	$1,075.22	$1,075.20	$1,075.20