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	$188.81	8.769%	$205.3667	$205.37	$205.35	$205.40
Purchase #2	$17.85	12.564%	$20.0927	$20.09	$20.10	$20.10
Purchase #3	$57.94	8.235%	$62.7114	$62.71	$62.70	$62.70
Purchase #4	$191.81	10.754%	$212.4372	$212.44	$212.45	$212.40
Purchase #5	$131.29	11.372%	$146.2203	$146.22	$146.20	$146.20
Purchase #6	$196.38	4.714%	$205.6374	$205.64	$205.65	$205.60
Purchase #7	$140.32	7.105%	$150.2897	$150.29	$150.30	$150.30
7 purchase totals =	$924.40		$1,002.7554	$1,002.76	$1,002.75	$1,002.70