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	$238.59	7.103%	$255.537	$255.54	$255.55	$255.50
Purchase #2	$5.52	6.388%	$5.8726	$5.87	$5.85	$5.90
Purchase #3	$97.52	6.867%	$104.2167	$104.22	$104.20	$104.20
Purchase #4	$153.94	8.256%	$166.6493	$166.65	$166.65	$166.60
Purchase #5	$215.84	13.127%	$244.1733	$244.17	$244.15	$244.20
Purchase #6	$99.82	12.674%	$112.4712	$112.47	$112.45	$112.50
Purchase #7	$39.97	4.719%	$41.8562	$41.86	$41.85	$41.90
7 purchase totals =	$851.20		$930.7763	$930.78	$930.70	$930.80