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	$176.43	4.153%	$183.7571	$183.76	$183.75	$183.80
Purchase #2	$185.67	7.651%	$199.8756	$199.88	$199.90	$199.90
Purchase #3	$234.73	12.325%	$263.6605	$263.66	$263.65	$263.70
Purchase #4	$12.76	9.751%	$14.0042	$14.00	$14.00	$14.00
Purchase #5	$164.81	10.244%	$181.6931	$181.69	$181.70	$181.70
Purchase #6	$16.25	12.554%	$18.29	$18.29	$18.30	$18.30
Purchase #7	$111.91	4.405%	$116.8396	$116.84	$116.85	$116.80
7 purchase totals =	$902.56		$978.1201	$978.12	$978.15	$978.20