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	$207.45	7.692%	$223.4071	$223.41	$223.40	$223.40
Purchase #2	$61.68	4.598%	$64.516	$64.52	$64.50	$64.50
Purchase #3	$203.93	9.806%	$223.9274	$223.93	$223.95	$223.90
Purchase #4	$158.93	12.393%	$178.6262	$178.63	$178.65	$178.60
Purchase #5	$147.72	8.359%	$160.0679	$160.07	$160.05	$160.10
Purchase #6	$34.82	11.252%	$38.7379	$38.74	$38.75	$38.70
Purchase #7	$119.87	6.439%	$127.5884	$127.59	$127.60	$127.60
7 purchase totals =	$934.40		$1,016.8709	$1,016.89	$1,016.90	$1,016.80