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	$230.72	4.221%	$240.4587	$240.46	$240.45	$240.50
Purchase #2	$136.47	11.303%	$151.8952	$151.90	$151.90	$151.90
Purchase #3	$42.41	9.208%	$46.3151	$46.32	$46.30	$46.30
Purchase #4	$132.60	10.289%	$146.2432	$146.24	$146.25	$146.20
Purchase #5	$207.39	4.117%	$215.9282	$215.93	$215.95	$215.90
Purchase #6	$83.31	6.554%	$88.7701	$88.77	$88.75	$88.80
Purchase #7	$145.81	8.104%	$157.6264	$157.63	$157.65	$157.60
7 purchase totals =	$978.71		$1,047.2369	$1,047.25	$1,047.25	$1,047.20