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	$97.30	8.834%	$105.8955	$105.90	$105.90	$105.90
Purchase #2	$38.86	12.418%	$43.6856	$43.69	$43.70	$43.70
Purchase #3	$133.55	12.528%	$150.2811	$150.28	$150.30	$150.30
Purchase #4	$116.32	8.717%	$126.4596	$126.46	$126.45	$126.50
Purchase #5	$49.48	12.411%	$55.621	$55.62	$55.60	$55.60
Purchase #6	$204.89	12.553%	$230.6098	$230.61	$230.60	$230.60
Purchase #7	$216.41	5.238%	$227.7456	$227.75	$227.75	$227.70
7 purchase totals =	$856.81		$940.2982	$940.31	$940.30	$940.30