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	$201.30	3.596%	$208.5387	$208.54	$208.55	$208.50
Purchase #2	$50.81	3.218%	$52.4451	$52.45	$52.45	$52.40
Purchase #3	$51.68	11.293%	$57.5162	$57.52	$57.50	$57.50
Purchase #4	$111.86	6.163%	$118.7539	$118.75	$118.75	$118.80
Purchase #5	$50.90	12.270%	$57.1454	$57.15	$57.15	$57.10
Purchase #6	$12.43	11.592%	$13.8709	$13.87	$13.85	$13.90
Purchase #7	$211.58	5.464%	$223.1407	$223.14	$223.15	$223.10
7 purchase totals =	$690.56		$731.4109	$731.42	$731.40	$731.30