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	$171.29	12.302%	$192.3621	$192.36	$192.35	$192.40
Purchase #2	$182.47	8.862%	$198.6405	$198.64	$198.65	$198.60
Purchase #3	$196.63	5.196%	$206.8469	$206.85	$206.85	$206.80
Purchase #4	$198.31	4.602%	$207.4362	$207.44	$207.45	$207.40
Purchase #5	$66.41	9.318%	$72.5981	$72.60	$72.60	$72.60
Purchase #6	$136.35	6.361%	$145.0232	$145.02	$145.00	$145.00
Purchase #7	$73.61	12.116%	$82.5286	$82.53	$82.55	$82.50
7 purchase totals =	$1,025.07		$1,105.4356	$1,105.44	$1,105.45	$1,105.30