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	$220.31	8.725%	$239.532	$239.53	$239.55	$239.50
Purchase #2	$148.41	11.457%	$165.4133	$165.41	$165.40	$165.40
Purchase #3	$68.45	5.806%	$72.4242	$72.42	$72.40	$72.40
Purchase #4	$164.40	4.402%	$171.6369	$171.64	$171.65	$171.60
Purchase #5	$52.43	9.602%	$57.4643	$57.46	$57.45	$57.50
Purchase #6	$39.35	10.256%	$43.3857	$43.39	$43.40	$43.40
Purchase #7	$221.85	7.222%	$237.872	$237.87	$237.85	$237.90
7 purchase totals =	$915.20		$987.7284	$987.72	$987.70	$987.70