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	$191.51	7.177%	$205.2547	$205.25	$205.25	$205.30
Purchase #2	$54.87	13.693%	$62.3833	$62.38	$62.40	$62.40
Purchase #3	$96.57	9.243%	$105.496	$105.50	$105.50	$105.50
Purchase #4	$177.39	5.427%	$187.017	$187.02	$187.00	$187.00
Purchase #5	$161.77	12.560%	$182.0883	$182.09	$182.10	$182.10
Purchase #6	$53.97	10.437%	$59.6028	$59.60	$59.60	$59.60
Purchase #7	$24.67	13.372%	$27.9689	$27.97	$27.95	$28.00
7 purchase totals =	$760.75		$829.8110	$829.81	$829.80	$829.90