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	$56.33	5.716%	$59.5498	$59.55	$59.55	$59.50
Purchase #2	$187.56	11.175%	$208.5198	$208.52	$208.50	$208.50
Purchase #3	$81.29	6.538%	$86.6047	$86.60	$86.60	$86.60
Purchase #4	$206.39	7.337%	$221.5328	$221.53	$221.55	$221.50
Purchase #5	$215.44	13.114%	$243.6928	$243.69	$243.70	$243.70
Purchase #6	$247.81	4.724%	$259.5165	$259.52	$259.50	$259.50
Purchase #7	$123.33	4.621%	$129.0291	$129.03	$129.05	$129.00
7 purchase totals =	$1,118.15		$1,208.4455	$1,208.44	$1,208.45	$1,208.30