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	$23.62	12.405%	$26.5501	$26.55	$26.55	$26.60
Purchase #2	$192.59	11.831%	$215.3753	$215.38	$215.40	$215.40
Purchase #3	$62.31	4.522%	$65.1277	$65.13	$65.15	$65.10
Purchase #4	$157.59	5.717%	$166.5994	$166.60	$166.60	$166.60
Purchase #5	$100.46	4.715%	$105.1967	$105.20	$105.20	$105.20
Purchase #6	$191.99	8.541%	$208.3879	$208.39	$208.40	$208.40
Purchase #7	$211.90	5.177%	$222.8701	$222.87	$222.85	$222.90
7 purchase totals =	$940.46		$1,010.1072	$1,010.12	$1,010.15	$1,010.20