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	$78.30	4.202%	$81.5902	$81.59	$81.60	$81.60
Purchase #2	$97.45	6.599%	$103.8807	$103.88	$103.90	$103.90
Purchase #3	$12.55	13.576%	$14.2538	$14.25	$14.25	$14.30
Purchase #4	$50.65	5.448%	$53.4094	$53.41	$53.40	$53.40
Purchase #5	$200.83	10.863%	$222.6462	$222.65	$222.65	$222.60
Purchase #6	$65.25	10.445%	$72.0654	$72.07	$72.05	$72.10
Purchase #7	$198.69	4.514%	$207.6589	$207.66	$207.65	$207.70
7 purchase totals =	$703.72		$755.5046	$755.51	$755.50	$755.60