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	$68.59	6.214%	$72.8522	$72.85	$72.85	$72.90
Purchase #2	$190.84	6.521%	$203.2847	$203.28	$203.30	$203.30
Purchase #3	$183.59	13.652%	$208.6537	$208.65	$208.65	$208.70
Purchase #4	$131.86	5.441%	$139.0345	$139.03	$139.05	$139.00
Purchase #5	$161.82	6.657%	$172.5924	$172.59	$172.60	$172.60
Purchase #6	$118.52	11.716%	$132.4058	$132.41	$132.40	$132.40
Purchase #7	$74.59	8.668%	$81.0555	$81.06	$81.05	$81.10
7 purchase totals =	$929.81		$1,009.8788	$1,009.87	$1,009.90	$1,010.00