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	$131.31	11.115%	$145.9051	$145.91	$145.90	$145.90
Purchase #2	$10.68	11.873%	$11.948	$11.95	$11.95	$11.90
Purchase #3	$121.42	10.787%	$134.5176	$134.52	$134.50	$134.50
Purchase #4	$199.83	11.743%	$223.296	$223.30	$223.30	$223.30
Purchase #5	$158.45	4.621%	$165.772	$165.77	$165.75	$165.80
Purchase #6	$215.53	3.628%	$223.3494	$223.35	$223.35	$223.30
Purchase #7	$56.92	10.396%	$62.8374	$62.84	$62.85	$62.80
7 purchase totals =	$894.14		$967.6255	$967.64	$967.60	$967.50