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	$120.69	8.138%	$130.5118	$130.51	$130.50	$130.50
Purchase #2	$131.26	13.508%	$148.9906	$148.99	$149.00	$149.00
Purchase #3	$12.91	13.170%	$14.6102	$14.61	$14.60	$14.60
Purchase #4	$137.51	3.699%	$142.5965	$142.60	$142.60	$142.60
Purchase #5	$241.84	13.656%	$274.8657	$274.87	$274.85	$274.90
Purchase #6	$20.37	5.501%	$21.4906	$21.49	$21.50	$21.50
Purchase #7	$181.90	8.214%	$196.8413	$196.84	$196.85	$196.80
7 purchase totals =	$846.48		$929.9067	$929.91	$929.90	$929.90