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	$208.28	10.800%	$230.7742	$230.77	$230.75	$230.80
Purchase #2	$10.61	12.503%	$11.9366	$11.94	$11.95	$11.90
Purchase #3	$162.79	3.687%	$168.7921	$168.79	$168.80	$168.80
Purchase #4	$164.36	4.400%	$171.5918	$171.59	$171.60	$171.60
Purchase #5	$173.50	12.328%	$194.8891	$194.89	$194.90	$194.90
Purchase #6	$224.30	9.358%	$245.29	$245.29	$245.30	$245.30
Purchase #7	$90.83	10.189%	$100.0847	$100.08	$100.10	$100.10
7 purchase totals =	$1,034.67		$1,123.3585	$1,123.35	$1,123.40	$1,123.40