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	$137.31	12.739%	$154.8019	$154.80	$154.80	$154.80
Purchase #2	$147.52	8.617%	$160.2318	$160.23	$160.25	$160.20
Purchase #3	$154.84	3.474%	$160.2191	$160.22	$160.20	$160.20
Purchase #4	$235.59	11.520%	$262.73	$262.73	$262.75	$262.70
Purchase #5	$120.45	9.553%	$131.9566	$131.96	$131.95	$132.00
Purchase #6	$235.25	3.568%	$243.6437	$243.64	$243.65	$243.60
Purchase #7	$74.58	10.579%	$82.4698	$82.47	$82.45	$82.50
7 purchase totals =	$1,105.54		$1,196.0529	$1,196.05	$1,196.05	$1,196.00