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	$146.58	5.828%	$155.1227	$155.12	$155.10	$155.10
Purchase #2	$82.49	8.336%	$89.3664	$89.37	$89.35	$89.40
Purchase #3	$10.64	12.481%	$11.968	$11.97	$11.95	$12.00
Purchase #4	$40.79	12.433%	$45.8614	$45.86	$45.85	$45.90
Purchase #5	$132.73	10.215%	$146.2884	$146.29	$146.30	$146.30
Purchase #6	$232.97	9.854%	$255.9269	$255.93	$255.95	$255.90
Purchase #7	$184.90	3.149%	$190.7225	$190.72	$190.70	$190.70
7 purchase totals =	$831.10		$895.2563	$895.26	$895.20	$895.30