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	$227.43	7.509%	$244.5077	$244.51	$244.50	$244.50
Purchase #2	$108.39	9.472%	$118.6567	$118.66	$118.65	$118.70
Purchase #3	$140.90	5.396%	$148.503	$148.50	$148.50	$148.50
Purchase #4	$172.60	5.539%	$182.1603	$182.16	$182.15	$182.20
Purchase #5	$148.60	10.869%	$164.7513	$164.75	$164.75	$164.80
Purchase #6	$120.55	11.542%	$134.4639	$134.46	$134.45	$134.50
Purchase #7	$98.60	12.856%	$111.276	$111.28	$111.30	$111.30
7 purchase totals =	$1,017.07		$1,104.3189	$1,104.32	$1,104.30	$1,104.50