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	$208.95	9.373%	$228.5349	$228.53	$228.55	$228.50
Purchase #2	$187.93	5.846%	$198.9164	$198.92	$198.90	$198.90
Purchase #3	$105.67	10.431%	$116.6924	$116.69	$116.70	$116.70
Purchase #4	$54.73	12.253%	$61.4361	$61.44	$61.45	$61.40
Purchase #5	$60.56	13.458%	$68.7102	$68.71	$68.70	$68.70
Purchase #6	$59.35	3.171%	$61.232	$61.23	$61.25	$61.20
Purchase #7	$162.31	10.310%	$179.0442	$179.04	$179.05	$179.00
7 purchase totals =	$839.50		$914.5662	$914.56	$914.60	$914.40