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	$119.28	3.612%	$123.5884	$123.59	$123.60	$123.60
Purchase #2	$82.78	8.149%	$89.5257	$89.53	$89.55	$89.50
Purchase #3	$207.64	12.770%	$234.1556	$234.16	$234.15	$234.20
Purchase #4	$62.42	13.641%	$70.9347	$70.93	$70.95	$70.90
Purchase #5	$129.60	8.651%	$140.8117	$140.81	$140.80	$140.80
Purchase #6	$13.84	13.794%	$15.7491	$15.75	$15.75	$15.70
Purchase #7	$53.27	7.730%	$57.3878	$57.39	$57.40	$57.40
7 purchase totals =	$668.83		$732.1530	$732.16	$732.20	$732.10