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	$40.75	7.487%	$43.801	$43.80	$43.80	$43.80
Purchase #2	$65.45	9.175%	$71.455	$71.46	$71.45	$71.50
Purchase #3	$241.40	3.126%	$248.9462	$248.95	$248.95	$248.90
Purchase #4	$68.98	13.384%	$78.2123	$78.21	$78.20	$78.20
Purchase #5	$119.52	8.435%	$129.6015	$129.60	$129.60	$129.60
Purchase #6	$60.38	7.715%	$65.0383	$65.04	$65.05	$65.00
Purchase #7	$51.92	7.315%	$55.7179	$55.72	$55.70	$55.70
7 purchase totals =	$648.40		$692.7722	$692.78	$692.75	$692.70