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	$82.84	3.379%	$85.6392	$85.64	$85.65	$85.60
Purchase #2	$112.92	9.571%	$123.7276	$123.73	$123.75	$123.70
Purchase #3	$101.68	9.200%	$111.0346	$111.03	$111.05	$111.00
Purchase #4	$161.38	9.399%	$176.5481	$176.55	$176.55	$176.50
Purchase #5	$57.63	10.562%	$63.7169	$63.72	$63.70	$63.70
Purchase #6	$87.50	4.381%	$91.3334	$91.33	$91.35	$91.30
Purchase #7	$114.73	4.863%	$120.3093	$120.31	$120.30	$120.30
7 purchase totals =	$718.68		$772.3091	$772.31	$772.35	$772.10