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	$42.84	13.111%	$48.4568	$48.46	$48.45	$48.50
Purchase #2	$126.86	5.139%	$133.3793	$133.38	$133.40	$133.40
Purchase #3	$116.87	5.734%	$123.5713	$123.57	$123.55	$123.60
Purchase #4	$81.99	13.611%	$93.1497	$93.15	$93.15	$93.10
Purchase #5	$10.68	10.260%	$11.7758	$11.78	$11.80	$11.80
Purchase #6	$42.85	6.229%	$45.5191	$45.52	$45.50	$45.50
Purchase #7	$179.84	10.822%	$199.3023	$199.30	$199.30	$199.30
7 purchase totals =	$601.93		$655.1543	$655.16	$655.15	$655.20