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	$247.31	13.510%	$280.7216	$280.72	$280.70	$280.70
Purchase #2	$37.76	8.105%	$40.8204	$40.82	$40.80	$40.80
Purchase #3	$228.35	6.424%	$243.0192	$243.02	$243.00	$243.00
Purchase #4	$102.77	4.443%	$107.3361	$107.34	$107.35	$107.30
Purchase #5	$174.86	4.495%	$182.72	$182.72	$182.70	$182.70
Purchase #6	$114.86	10.730%	$127.1845	$127.18	$127.20	$127.20
Purchase #7	$181.29	3.205%	$187.1003	$187.10	$187.10	$187.10
7 purchase totals =	$1,087.20		$1,168.9021	$1,168.90	$1,168.85	$1,168.80