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	$196.54	6.151%	$208.6292	$208.63	$208.65	$208.60
Purchase #2	$116.91	5.677%	$123.547	$123.55	$123.55	$123.50
Purchase #3	$22.49	13.627%	$25.5547	$25.55	$25.55	$25.60
Purchase #4	$231.52	8.532%	$251.2733	$251.27	$251.25	$251.30
Purchase #5	$137.96	3.675%	$143.03	$143.03	$143.05	$143.00
Purchase #6	$240.72	10.445%	$265.8632	$265.86	$265.85	$265.90
Purchase #7	$218.44	10.533%	$241.4483	$241.45	$241.45	$241.40
7 purchase totals =	$1,164.58		$1,259.3457	$1,259.34	$1,259.35	$1,259.30