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	$176.93	10.354%	$195.2493	$195.25	$195.25	$195.20
Purchase #2	$11.94	8.706%	$12.9795	$12.98	$13.00	$13.00
Purchase #3	$190.73	10.798%	$211.325	$211.33	$211.35	$211.30
Purchase #4	$105.88	5.125%	$111.3064	$111.31	$111.30	$111.30
Purchase #5	$113.59	6.158%	$120.5849	$120.58	$120.60	$120.60
Purchase #6	$55.92	11.716%	$62.4716	$62.47	$62.45	$62.50
Purchase #7	$87.59	9.558%	$95.9619	$95.96	$95.95	$96.00
7 purchase totals =	$742.58		$809.8786	$809.88	$809.90	$809.90