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	$40.79	9.164%	$44.528	$44.53	$44.55	$44.50
Purchase #2	$28.31	12.831%	$31.9425	$31.94	$31.95	$31.90
Purchase #3	$66.29	13.225%	$75.0569	$75.06	$75.05	$75.10
Purchase #4	$80.92	10.623%	$89.5161	$89.52	$89.50	$89.50
Purchase #5	$132.32	13.835%	$150.6265	$150.63	$150.65	$150.60
Purchase #6	$151.44	4.545%	$158.3229	$158.32	$158.30	$158.30
Purchase #7	$48.67	5.837%	$51.5109	$51.51	$51.50	$51.50
7 purchase totals =	$548.74		$601.5038	$601.51	$601.50	$601.40