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	$208.77	13.330%	$236.599	$236.60	$236.60	$236.60
Purchase #2	$150.50	8.437%	$163.1977	$163.20	$163.20	$163.20
Purchase #3	$172.94	13.434%	$196.1728	$196.17	$196.15	$196.20
Purchase #4	$28.61	13.756%	$32.5456	$32.55	$32.55	$32.50
Purchase #5	$240.38	6.355%	$255.6561	$255.66	$255.65	$255.70
Purchase #6	$109.72	12.855%	$123.8245	$123.82	$123.80	$123.80
Purchase #7	$18.44	6.472%	$19.6334	$19.63	$19.65	$19.60
7 purchase totals =	$929.36		$1,027.6291	$1,027.63	$1,027.60	$1,027.60