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	$113.27	3.283%	$116.9887	$116.99	$117.00	$117.00
Purchase #2	$40.56	7.519%	$43.6097	$43.61	$43.60	$43.60
Purchase #3	$182.27	13.787%	$207.3996	$207.40	$207.40	$207.40
Purchase #4	$205.51	8.567%	$223.116	$223.12	$223.10	$223.10
Purchase #5	$29.60	6.233%	$31.445	$31.45	$31.45	$31.40
Purchase #6	$82.59	9.712%	$90.6111	$90.61	$90.60	$90.60
Purchase #7	$197.60	12.549%	$222.3968	$222.40	$222.40	$222.40
7 purchase totals =	$851.40		$935.5669	$935.58	$935.55	$935.50