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	$107.61	9.452%	$117.7813	$117.78	$117.80	$117.80
Purchase #2	$93.86	5.231%	$98.7698	$98.77	$98.75	$98.80
Purchase #3	$155.89	6.556%	$166.1101	$166.11	$166.10	$166.10
Purchase #4	$16.89	10.839%	$18.7207	$18.72	$18.70	$18.70
Purchase #5	$112.73	9.657%	$123.6163	$123.62	$123.60	$123.60
Purchase #6	$110.37	5.652%	$116.6081	$116.61	$116.60	$116.60
Purchase #7	$100.49	10.434%	$110.9751	$110.98	$111.00	$111.00
7 purchase totals =	$697.84		$752.5814	$752.59	$752.55	$752.60