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	$80.77	10.747%	$89.4504	$89.45	$89.45	$89.50
Purchase #2	$71.27	10.757%	$78.9365	$78.94	$78.95	$78.90
Purchase #3	$43.58	4.321%	$45.4631	$45.46	$45.45	$45.50
Purchase #4	$238.86	7.160%	$255.9624	$255.96	$255.95	$256.00
Purchase #5	$92.46	5.671%	$97.7034	$97.70	$97.70	$97.70
Purchase #6	$238.47	8.566%	$258.8973	$258.90	$258.90	$258.90
Purchase #7	$193.87	8.835%	$210.9984	$211.00	$211.00	$211.00
7 purchase totals =	$959.28		$1,037.4115	$1,037.41	$1,037.40	$1,037.50