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	$11.95	4.308%	$12.4648	$12.46	$12.45	$12.50
Purchase #2	$65.85	9.195%	$71.9049	$71.90	$71.90	$71.90
Purchase #3	$148.58	6.556%	$158.3209	$158.32	$158.30	$158.30
Purchase #4	$197.78	9.795%	$217.1526	$217.15	$217.15	$217.20
Purchase #5	$41.92	4.223%	$43.6903	$43.69	$43.70	$43.70
Purchase #6	$165.91	6.521%	$176.729	$176.73	$176.75	$176.70
Purchase #7	$11.32	12.305%	$12.7129	$12.71	$12.70	$12.70
7 purchase totals =	$643.31		$692.9754	$692.96	$692.95	$693.00