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	$125.84	12.407%	$141.453	$141.45	$141.45	$141.50
Purchase #2	$111.31	10.677%	$123.1946	$123.19	$123.20	$123.20
Purchase #3	$7.35	3.360%	$7.597	$7.60	$7.60	$7.60
Purchase #4	$62.30	10.652%	$68.9362	$68.94	$68.95	$68.90
Purchase #5	$55.56	10.611%	$61.4555	$61.46	$61.45	$61.50
Purchase #6	$25.89	10.151%	$28.5181	$28.52	$28.50	$28.50
Purchase #7	$179.77	9.810%	$197.4054	$197.41	$197.40	$197.40
7 purchase totals =	$568.02		$628.5598	$628.57	$628.55	$628.60