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	$69.55	9.647%	$76.2595	$76.26	$76.25	$76.30
Purchase #2	$58.90	4.444%	$61.5175	$61.52	$61.50	$61.50
Purchase #3	$176.60	13.656%	$200.7165	$200.72	$200.70	$200.70
Purchase #4	$12.75	4.672%	$13.3457	$13.35	$13.35	$13.30
Purchase #5	$103.66	7.116%	$111.0364	$111.04	$111.05	$111.00
Purchase #6	$123.84	12.408%	$139.2061	$139.21	$139.20	$139.20
Purchase #7	$43.85	8.137%	$47.4181	$47.42	$47.40	$47.40
7 purchase totals =	$589.15		$649.4998	$649.52	$649.45	$649.40