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	$175.45	12.247%	$196.9374	$196.94	$196.95	$196.90
Purchase #2	$116.85	10.151%	$128.7114	$128.71	$128.70	$128.70
Purchase #3	$34.60	10.506%	$38.2351	$38.24	$38.25	$38.20
Purchase #4	$23.69	13.527%	$26.8945	$26.89	$26.90	$26.90
Purchase #5	$240.95	8.474%	$261.3681	$261.37	$261.35	$261.40
Purchase #6	$188.28	12.838%	$212.4514	$212.45	$212.45	$212.50
Purchase #7	$103.96	10.540%	$114.9174	$114.92	$114.90	$114.90
7 purchase totals =	$883.78		$979.5153	$979.52	$979.50	$979.50