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	$53.80	9.806%	$59.0756	$59.08	$59.10	$59.10
Purchase #2	$157.42	12.745%	$177.4832	$177.48	$177.50	$177.50
Purchase #3	$169.61	10.339%	$187.146	$187.15	$187.15	$187.10
Purchase #4	$116.70	5.119%	$122.6739	$122.67	$122.65	$122.70
Purchase #5	$150.61	8.463%	$163.3561	$163.36	$163.35	$163.40
Purchase #6	$114.94	10.822%	$127.3788	$127.38	$127.40	$127.40
Purchase #7	$99.59	11.585%	$111.1275	$111.13	$111.15	$111.10
7 purchase totals =	$862.67		$948.2411	$948.25	$948.30	$948.30