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	$162.49	4.329%	$169.5242	$169.52	$169.50	$169.50
Purchase #2	$199.27	13.331%	$225.8347	$225.83	$225.85	$225.80
Purchase #3	$240.29	4.827%	$251.8888	$251.89	$251.90	$251.90
Purchase #4	$74.62	10.533%	$82.4797	$82.48	$82.50	$82.50
Purchase #5	$55.55	9.748%	$60.965	$60.97	$60.95	$61.00
Purchase #6	$148.48	12.192%	$166.5827	$166.58	$166.60	$166.60
Purchase #7	$44.31	8.747%	$48.1858	$48.19	$48.20	$48.20
7 purchase totals =	$925.01		$1,005.4609	$1,005.46	$1,005.50	$1,005.50