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	$229.98	5.146%	$241.8148	$241.81	$241.80	$241.80
Purchase #2	$161.63	7.488%	$173.7329	$173.73	$173.75	$173.70
Purchase #3	$41.44	13.630%	$47.0883	$47.09	$47.10	$47.10
Purchase #4	$140.52	4.257%	$146.5019	$146.50	$146.50	$146.50
Purchase #5	$89.95	3.181%	$92.8113	$92.81	$92.80	$92.80
Purchase #6	$92.80	8.342%	$100.5414	$100.54	$100.55	$100.50
Purchase #7	$105.95	6.296%	$112.6206	$112.62	$112.60	$112.60
7 purchase totals =	$862.27		$915.1112	$915.10	$915.10	$915.00