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	$166.71	5.716%	$176.2391	$176.24	$176.25	$176.20
Purchase #2	$104.49	6.779%	$111.5734	$111.57	$111.55	$111.60
Purchase #3	$182.52	12.668%	$205.6416	$205.64	$205.65	$205.60
Purchase #4	$54.25	9.591%	$59.4531	$59.45	$59.45	$59.50
Purchase #5	$96.52	4.110%	$100.487	$100.49	$100.50	$100.50
Purchase #6	$142.35	3.207%	$146.9152	$146.92	$146.90	$146.90
Purchase #7	$96.56	8.854%	$105.1094	$105.11	$105.10	$105.10
7 purchase totals =	$843.40		$905.4188	$905.42	$905.40	$905.40