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	$192.71	8.205%	$208.5219	$208.52	$208.50	$208.50
Purchase #2	$9.90	10.435%	$10.9331	$10.93	$10.95	$10.90
Purchase #3	$122.77	4.781%	$128.6396	$128.64	$128.65	$128.60
Purchase #4	$148.82	5.237%	$156.6137	$156.61	$156.60	$156.60
Purchase #5	$70.89	9.619%	$77.7089	$77.71	$77.70	$77.70
Purchase #6	$177.70	11.696%	$198.4838	$198.48	$198.50	$198.50
Purchase #7	$147.64	13.436%	$167.4769	$167.48	$167.50	$167.50
7 purchase totals =	$870.43		$948.3779	$948.37	$948.40	$948.30