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	$224.78	10.391%	$248.1369	$248.14	$248.15	$248.10
Purchase #2	$64.45	3.202%	$66.5137	$66.51	$66.50	$66.50
Purchase #3	$75.43	5.252%	$79.3916	$79.39	$79.40	$79.40
Purchase #4	$173.44	9.636%	$190.1527	$190.15	$190.15	$190.20
Purchase #5	$95.93	7.536%	$103.1593	$103.16	$103.15	$103.20
Purchase #6	$131.66	10.641%	$145.6699	$145.67	$145.65	$145.70
Purchase #7	$89.42	12.846%	$100.9069	$100.91	$100.90	$100.90
7 purchase totals =	$855.11		$933.9310	$933.93	$933.90	$934.00