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	$216.52	9.693%	$237.5073	$237.51	$237.50	$237.50
Purchase #2	$40.31	9.597%	$44.1786	$44.18	$44.20	$44.20
Purchase #3	$124.89	4.714%	$130.7773	$130.78	$130.80	$130.80
Purchase #4	$122.52	7.176%	$131.312	$131.31	$131.30	$131.30
Purchase #5	$51.77	9.244%	$56.5556	$56.56	$56.55	$56.60
Purchase #6	$183.32	8.545%	$198.9847	$198.98	$199.00	$199.00
Purchase #7	$50.36	13.303%	$57.0594	$57.06	$57.05	$57.10
7 purchase totals =	$789.69		$856.3749	$856.38	$856.40	$856.50