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	$101.85	3.789%	$105.7091	$105.71	$105.70	$105.70
Purchase #2	$109.92	9.314%	$120.1579	$120.16	$120.15	$120.20
Purchase #3	$184.59	8.549%	$200.3706	$200.37	$200.35	$200.40
Purchase #4	$217.27	7.631%	$233.8499	$233.85	$233.85	$233.80
Purchase #5	$192.99	12.225%	$216.583	$216.58	$216.60	$216.60
Purchase #6	$127.67	13.404%	$144.7829	$144.78	$144.80	$144.80
Purchase #7	$103.33	7.576%	$111.1583	$111.16	$111.15	$111.20
7 purchase totals =	$1,037.62		$1,132.6117	$1,132.61	$1,132.60	$1,132.70