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	$142.52	9.234%	$155.6803	$155.68	$155.70	$155.70
Purchase #2	$97.93	13.758%	$111.4032	$111.40	$111.40	$111.40
Purchase #3	$176.82	11.286%	$196.7759	$196.78	$196.80	$196.80
Purchase #4	$181.96	9.595%	$199.4191	$199.42	$199.40	$199.40
Purchase #5	$96.95	7.231%	$103.9605	$103.96	$103.95	$104.00
Purchase #6	$17.80	10.342%	$19.6409	$19.64	$19.65	$19.60
Purchase #7	$206.55	12.589%	$232.5526	$232.55	$232.55	$232.60
7 purchase totals =	$920.53		$1,019.4325	$1,019.43	$1,019.45	$1,019.50