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	$134.80	13.176%	$152.5612	$152.56	$152.55	$152.60
Purchase #2	$209.87	5.437%	$221.2806	$221.28	$221.30	$221.30
Purchase #3	$148.42	13.387%	$168.289	$168.29	$168.30	$168.30
Purchase #4	$222.76	12.683%	$251.0127	$251.01	$251.00	$251.00
Purchase #5	$63.30	6.680%	$67.5284	$67.53	$67.55	$67.50
Purchase #6	$140.62	12.772%	$158.58	$158.58	$158.60	$158.60
Purchase #7	$60.75	6.181%	$64.505	$64.51	$64.50	$64.50
7 purchase totals =	$980.52		$1,083.7569	$1,083.76	$1,083.80	$1,083.80