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	$149.50	7.419%	$160.5914	$160.59	$160.60	$160.60
Purchase #2	$216.70	9.126%	$236.476	$236.48	$236.50	$236.50
Purchase #3	$111.72	5.467%	$117.8277	$117.83	$117.85	$117.80
Purchase #4	$178.39	10.840%	$197.7275	$197.73	$197.75	$197.70
Purchase #5	$73.73	12.698%	$83.0922	$83.09	$83.10	$83.10
Purchase #6	$87.45	10.359%	$96.5089	$96.51	$96.50	$96.50
Purchase #7	$154.68	9.117%	$168.7822	$168.78	$168.80	$168.80
7 purchase totals =	$972.17		$1,061.0059	$1,061.01	$1,061.10	$1,061.00