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	$181.72	10.348%	$200.5244	$200.52	$200.50	$200.50
Purchase #2	$77.51	3.464%	$80.1949	$80.19	$80.20	$80.20
Purchase #3	$174.86	4.842%	$183.3267	$183.33	$183.35	$183.30
Purchase #4	$76.91	4.610%	$80.4556	$80.46	$80.45	$80.50
Purchase #5	$157.62	9.178%	$172.0864	$172.09	$172.10	$172.10
Purchase #6	$214.47	5.705%	$226.7055	$226.71	$226.70	$226.70
Purchase #7	$55.40	10.242%	$61.0741	$61.07	$61.05	$61.10
7 purchase totals =	$938.49		$1,004.3676	$1,004.37	$1,004.35	$1,004.40