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	$233.63	9.536%	$255.909	$255.91	$255.90	$255.90
Purchase #2	$70.59	11.154%	$78.4636	$78.46	$78.45	$78.50
Purchase #3	$149.55	3.294%	$154.4762	$154.48	$154.50	$154.50
Purchase #4	$145.27	9.239%	$158.6915	$158.69	$158.70	$158.70
Purchase #5	$248.47	5.430%	$261.9619	$261.96	$261.95	$262.00
Purchase #6	$208.78	4.597%	$218.3776	$218.38	$218.40	$218.40
Purchase #7	$40.79	12.251%	$45.7872	$45.79	$45.80	$45.80
7 purchase totals =	$1,097.08		$1,173.6670	$1,173.67	$1,173.70	$1,173.80