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	$92.71	11.720%	$103.5756	$103.58	$103.60	$103.60
Purchase #2	$161.27	6.844%	$172.3073	$172.31	$172.30	$172.30
Purchase #3	$206.96	10.507%	$228.7053	$228.71	$228.70	$228.70
Purchase #4	$51.82	11.151%	$57.5984	$57.60	$57.60	$57.60
Purchase #5	$243.58	5.611%	$257.2473	$257.25	$257.25	$257.20
Purchase #6	$100.59	11.351%	$112.008	$112.01	$112.00	$112.00
Purchase #7	$126.69	6.618%	$135.0743	$135.07	$135.05	$135.10
7 purchase totals =	$983.62		$1,066.5162	$1,066.53	$1,066.50	$1,066.50