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	$36.26	11.563%	$40.4527	$40.45	$40.45	$40.50
Purchase #2	$58.82	13.417%	$66.7119	$66.71	$66.70	$66.70
Purchase #3	$244.55	4.336%	$255.1537	$255.15	$255.15	$255.20
Purchase #4	$164.71	9.780%	$180.8186	$180.82	$180.80	$180.80
Purchase #5	$211.85	5.376%	$223.2391	$223.24	$223.25	$223.20
Purchase #6	$150.66	3.314%	$155.6529	$155.65	$155.65	$155.70
Purchase #7	$38.84	3.183%	$40.0763	$40.08	$40.10	$40.10
7 purchase totals =	$905.69		$962.1052	$962.10	$962.10	$962.20