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	$87.39	3.218%	$90.2022	$90.20	$90.20	$90.20
Purchase #2	$83.82	4.118%	$87.2717	$87.27	$87.25	$87.30
Purchase #3	$197.82	3.694%	$205.1275	$205.13	$205.15	$205.10
Purchase #4	$78.70	7.368%	$84.4986	$84.50	$84.50	$84.50
Purchase #5	$129.49	10.493%	$143.0774	$143.08	$143.10	$143.10
Purchase #6	$207.84	7.546%	$223.5236	$223.52	$223.50	$223.50
Purchase #7	$160.77	4.159%	$167.4564	$167.46	$167.45	$167.50
7 purchase totals =	$945.83		$1,001.1574	$1,001.16	$1,001.15	$1,001.20