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	$217.77	6.462%	$231.8423	$231.84	$231.85	$231.80
Purchase #2	$87.57	3.514%	$90.6472	$90.65	$90.65	$90.60
Purchase #3	$101.32	4.393%	$105.771	$105.77	$105.75	$105.80
Purchase #4	$79.95	13.152%	$90.465	$90.47	$90.45	$90.50
Purchase #5	$72.71	9.713%	$79.7723	$79.77	$79.75	$79.80
Purchase #6	$197.70	8.161%	$213.8343	$213.83	$213.85	$213.80
Purchase #7	$236.88	7.335%	$254.2551	$254.26	$254.25	$254.30
7 purchase totals =	$993.90		$1,066.5872	$1,066.59	$1,066.55	$1,066.60