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	$53.87	10.757%	$59.6648	$59.66	$59.65	$59.70
Purchase #2	$147.60	4.394%	$154.0855	$154.09	$154.10	$154.10
Purchase #3	$178.79	5.729%	$189.0329	$189.03	$189.05	$189.00
Purchase #4	$145.30	8.744%	$158.005	$158.01	$158.00	$158.00
Purchase #5	$203.57	3.490%	$210.6746	$210.67	$210.65	$210.70
Purchase #6	$66.47	9.748%	$72.9495	$72.95	$72.95	$72.90
Purchase #7	$94.63	6.641%	$100.9144	$100.91	$100.90	$100.90
7 purchase totals =	$890.23		$945.3267	$945.32	$945.30	$945.30