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	$229.43	12.691%	$258.547	$258.55	$258.55	$258.50
Purchase #2	$40.29	10.392%	$44.4769	$44.48	$44.50	$44.50
Purchase #3	$83.94	6.685%	$89.5514	$89.55	$89.55	$89.60
Purchase #4	$225.43	13.817%	$256.5777	$256.58	$256.60	$256.60
Purchase #5	$146.94	9.585%	$161.0242	$161.02	$161.00	$161.00
Purchase #6	$59.46	4.551%	$62.166	$62.17	$62.15	$62.20
Purchase #7	$127.32	12.839%	$143.6666	$143.67	$143.65	$143.70
7 purchase totals =	$912.81		$1,016.0098	$1,016.02	$1,016.00	$1,016.10