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	$116.87	12.608%	$131.605	$131.61	$131.60	$131.60
Purchase #2	$246.60	5.307%	$259.6871	$259.69	$259.70	$259.70
Purchase #3	$213.70	3.462%	$221.0983	$221.10	$221.10	$221.10
Purchase #4	$109.67	12.218%	$123.0695	$123.07	$123.05	$123.10
Purchase #5	$194.25	6.826%	$207.5095	$207.51	$207.50	$207.50
Purchase #6	$105.72	3.519%	$109.4403	$109.44	$109.45	$109.40
Purchase #7	$31.96	5.744%	$33.7958	$33.80	$33.80	$33.80
7 purchase totals =	$1,018.77		$1,086.2055	$1,086.22	$1,086.20	$1,086.20