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	$49.80	13.114%	$56.3308	$56.33	$56.35	$56.30
Purchase #2	$85.93	5.444%	$90.608	$90.61	$90.60	$90.60
Purchase #3	$75.45	13.232%	$85.4335	$85.43	$85.45	$85.40
Purchase #4	$134.65	3.626%	$139.5324	$139.53	$139.55	$139.50
Purchase #5	$184.94	7.605%	$199.0047	$199.00	$199.00	$199.00
Purchase #6	$151.38	11.828%	$169.2852	$169.29	$169.30	$169.30
Purchase #7	$18.32	5.833%	$19.3886	$19.39	$19.40	$19.40
7 purchase totals =	$700.47		$759.5832	$759.58	$759.65	$759.50