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	$200.47	6.548%	$213.5968	$213.60	$213.60	$213.60
Purchase #2	$62.30	13.273%	$70.5691	$70.57	$70.55	$70.60
Purchase #3	$135.59	11.490%	$151.1693	$151.17	$151.15	$151.20
Purchase #4	$75.45	3.668%	$78.2175	$78.22	$78.20	$78.20
Purchase #5	$188.71	10.521%	$208.5642	$208.56	$208.55	$208.60
Purchase #6	$207.64	9.120%	$226.5768	$226.58	$226.60	$226.60
Purchase #7	$199.71	11.448%	$222.5728	$222.57	$222.55	$222.60
7 purchase totals =	$1,069.87		$1,171.2665	$1,171.27	$1,171.20	$1,171.40