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	$204.94	4.602%	$214.3713	$214.37	$214.35	$214.40
Purchase #2	$11.56	13.562%	$13.1278	$13.13	$13.15	$13.10
Purchase #3	$183.28	8.286%	$198.4666	$198.47	$198.45	$198.50
Purchase #4	$99.34	4.234%	$103.5461	$103.55	$103.55	$103.50
Purchase #5	$181.86	12.748%	$205.0435	$205.04	$205.05	$205.00
Purchase #6	$90.96	8.396%	$98.597	$98.60	$98.60	$98.60
Purchase #7	$11.28	10.367%	$12.4494	$12.45	$12.45	$12.40
7 purchase totals =	$783.22		$845.6017	$845.61	$845.60	$845.50