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	$79.43	9.141%	$86.6907	$86.69	$86.70	$86.70
Purchase #2	$68.63	13.659%	$78.0042	$78.00	$78.00	$78.00
Purchase #3	$51.69	6.467%	$55.0328	$55.03	$55.05	$55.00
Purchase #4	$14.38	7.705%	$15.488	$15.49	$15.50	$15.50
Purchase #5	$142.52	8.552%	$154.7083	$154.71	$154.70	$154.70
Purchase #6	$105.86	5.152%	$111.3139	$111.31	$111.30	$111.30
Purchase #7	$250.47	12.396%	$281.5183	$281.52	$281.50	$281.50
7 purchase totals =	$712.98		$782.7562	$782.75	$782.75	$782.70