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	$214.84	5.724%	$227.1374	$227.14	$227.15	$227.10
Purchase #2	$228.60	9.561%	$250.4564	$250.46	$250.45	$250.50
Purchase #3	$125.28	11.287%	$139.4204	$139.42	$139.40	$139.40
Purchase #4	$36.73	8.134%	$39.7176	$39.72	$39.70	$39.70
Purchase #5	$42.53	7.183%	$45.5849	$45.58	$45.60	$45.60
Purchase #6	$175.33	4.418%	$183.0761	$183.08	$183.10	$183.10
Purchase #7	$71.47	7.832%	$77.0675	$77.07	$77.05	$77.10
7 purchase totals =	$894.78		$962.4603	$962.47	$962.45	$962.50