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	$184.50	11.547%	$205.8042	$205.80	$205.80	$205.80
Purchase #2	$87.49	10.722%	$96.8707	$96.87	$96.85	$96.90
Purchase #3	$112.54	9.531%	$123.2662	$123.27	$123.25	$123.30
Purchase #4	$189.60	3.455%	$196.1507	$196.15	$196.15	$196.20
Purchase #5	$165.75	11.562%	$184.914	$184.91	$184.90	$184.90
Purchase #6	$132.69	3.375%	$137.1683	$137.17	$137.15	$137.20
Purchase #7	$13.65	5.721%	$14.4309	$14.43	$14.45	$14.40
7 purchase totals =	$886.22		$958.6050	$958.60	$958.55	$958.70