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	$221.73	7.716%	$238.8387	$238.84	$238.85	$238.80
Purchase #2	$174.47	7.252%	$187.1226	$187.12	$187.10	$187.10
Purchase #3	$18.87	13.301%	$21.3799	$21.38	$21.40	$21.40
Purchase #4	$117.32	5.572%	$123.8571	$123.86	$123.85	$123.90
Purchase #5	$18.75	3.641%	$19.4327	$19.43	$19.45	$19.40
Purchase #6	$181.58	13.426%	$205.9589	$205.96	$205.95	$206.00
Purchase #7	$131.47	4.572%	$137.4808	$137.48	$137.50	$137.50
7 purchase totals =	$864.19		$934.0707	$934.07	$934.10	$934.10