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	$163.81	13.253%	$185.5197	$185.52	$185.50	$185.50
Purchase #2	$43.55	11.706%	$48.648	$48.65	$48.65	$48.60
Purchase #3	$11.43	10.865%	$12.6719	$12.67	$12.65	$12.70
Purchase #4	$50.44	3.371%	$52.1403	$52.14	$52.15	$52.10
Purchase #5	$167.76	4.630%	$175.5273	$175.53	$175.55	$175.50
Purchase #6	$48.60	11.601%	$54.2381	$54.24	$54.25	$54.20
Purchase #7	$239.43	8.244%	$259.1686	$259.17	$259.15	$259.20
7 purchase totals =	$725.02		$787.9139	$787.92	$787.90	$787.80