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	$197.60	3.820%	$205.1483	$205.15	$205.15	$205.10
Purchase #2	$235.96	8.260%	$255.4503	$255.45	$255.45	$255.50
Purchase #3	$41.46	5.486%	$43.7345	$43.73	$43.75	$43.70
Purchase #4	$128.89	8.152%	$139.3971	$139.40	$139.40	$139.40
Purchase #5	$30.41	4.293%	$31.7155	$31.72	$31.70	$31.70
Purchase #6	$155.37	13.545%	$176.4149	$176.41	$176.40	$176.40
Purchase #7	$148.38	8.275%	$160.6584	$160.66	$160.65	$160.70
7 purchase totals =	$938.07		$1,012.5190	$1,012.52	$1,012.50	$1,012.50