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	$142.82	4.763%	$149.6225	$149.62	$149.60	$149.60
Purchase #2	$202.70	10.425%	$223.8315	$223.83	$223.85	$223.80
Purchase #3	$85.74	5.750%	$90.6701	$90.67	$90.65	$90.70
Purchase #4	$43.62	7.446%	$46.8679	$46.87	$46.85	$46.90
Purchase #5	$148.52	12.846%	$167.5989	$167.60	$167.60	$167.60
Purchase #6	$123.92	7.290%	$132.9538	$132.95	$132.95	$133.00
Purchase #7	$186.52	5.160%	$196.1444	$196.14	$196.15	$196.10
7 purchase totals =	$933.84		$1,007.6891	$1,007.68	$1,007.65	$1,007.70