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	$121.94	8.675%	$132.5183	$132.52	$132.50	$132.50
Purchase #2	$126.47	5.646%	$133.6105	$133.61	$133.60	$133.60
Purchase #3	$248.72	4.294%	$259.4	$259.40	$259.40	$259.40
Purchase #4	$37.91	9.277%	$41.4269	$41.43	$41.45	$41.40
Purchase #5	$114.31	4.421%	$119.3636	$119.36	$119.35	$119.40
Purchase #6	$53.95	13.750%	$61.3681	$61.37	$61.35	$61.40
Purchase #7	$153.65	13.823%	$174.889	$174.89	$174.90	$174.90
7 purchase totals =	$856.95		$922.5764	$922.58	$922.55	$922.60