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	$180.66	13.252%	$204.6011	$204.60	$204.60	$204.60
Purchase #2	$134.82	5.327%	$142.0019	$142.00	$142.00	$142.00
Purchase #3	$66.35	11.338%	$73.8728	$73.87	$73.85	$73.90
Purchase #4	$180.37	10.280%	$198.912	$198.91	$198.90	$198.90
Purchase #5	$120.98	5.349%	$127.4512	$127.45	$127.45	$127.50
Purchase #6	$201.84	6.636%	$215.2341	$215.23	$215.25	$215.20
Purchase #7	$126.66	6.461%	$134.8435	$134.84	$134.85	$134.80
7 purchase totals =	$1,011.68		$1,096.9166	$1,096.90	$1,096.90	$1,096.90