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	$244.81	3.795%	$254.1005	$254.10	$254.10	$254.10
Purchase #2	$5.42	3.620%	$5.6162	$5.62	$5.60	$5.60
Purchase #3	$151.72	13.687%	$172.4859	$172.49	$172.50	$172.50
Purchase #4	$108.68	9.178%	$118.6547	$118.65	$118.65	$118.70
Purchase #5	$144.55	8.330%	$156.591	$156.59	$156.60	$156.60
Purchase #6	$117.75	8.276%	$127.495	$127.50	$127.50	$127.50
Purchase #7	$230.31	3.703%	$238.8384	$238.84	$238.85	$238.80
7 purchase totals =	$1,003.24		$1,073.7817	$1,073.79	$1,073.80	$1,073.80