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	$92.40	9.469%	$101.1494	$101.15	$101.15	$101.10
Purchase #2	$8.31	9.863%	$9.1296	$9.13	$9.15	$9.10
Purchase #3	$137.45	9.544%	$150.5682	$150.57	$150.55	$150.60
Purchase #4	$52.59	13.832%	$59.8642	$59.86	$59.85	$59.90
Purchase #5	$184.44	12.606%	$207.6905	$207.69	$207.70	$207.70
Purchase #6	$96.39	4.143%	$100.3834	$100.38	$100.40	$100.40
Purchase #7	$73.64	10.463%	$81.345	$81.35	$81.35	$81.30
7 purchase totals =	$645.22		$710.1303	$710.13	$710.15	$710.10