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	$214.41	6.616%	$228.5954	$228.60	$228.60	$228.60
Purchase #2	$96.52	3.610%	$100.0044	$100.00	$100.00	$100.00
Purchase #3	$169.57	12.565%	$190.8765	$190.88	$190.90	$190.90
Purchase #4	$185.64	3.323%	$191.8088	$191.81	$191.80	$191.80
Purchase #5	$20.87	11.136%	$23.1941	$23.19	$23.20	$23.20
Purchase #6	$197.51	6.263%	$209.8801	$209.88	$209.90	$209.90
Purchase #7	$111.63	10.565%	$123.4237	$123.42	$123.40	$123.40
7 purchase totals =	$996.15		$1,067.7830	$1,067.78	$1,067.80	$1,067.80