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	$139.62	3.522%	$144.5374	$144.54	$144.55	$144.50
Purchase #2	$186.88	11.376%	$208.1395	$208.14	$208.15	$208.10
Purchase #3	$103.48	12.320%	$116.2287	$116.23	$116.25	$116.20
Purchase #4	$132.69	9.477%	$145.265	$145.27	$145.25	$145.30
Purchase #5	$59.45	11.459%	$66.2624	$66.26	$66.25	$66.30
Purchase #6	$207.29	7.693%	$223.2368	$223.24	$223.25	$223.20
Purchase #7	$156.85	5.448%	$165.3952	$165.40	$165.40	$165.40
7 purchase totals =	$986.26		$1,069.0650	$1,069.08	$1,069.10	$1,069.00