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	$218.73	10.589%	$241.8913	$241.89	$241.90	$241.90
Purchase #2	$28.80	6.854%	$30.774	$30.77	$30.75	$30.80
Purchase #3	$32.70	11.626%	$36.5017	$36.50	$36.50	$36.50
Purchase #4	$42.38	7.757%	$45.6674	$45.67	$45.65	$45.70
Purchase #5	$62.53	5.851%	$66.1886	$66.19	$66.20	$66.20
Purchase #6	$163.27	9.565%	$178.8868	$178.89	$178.90	$178.90
Purchase #7	$136.41	4.189%	$142.1242	$142.12	$142.10	$142.10
7 purchase totals =	$684.82		$742.0340	$742.03	$742.00	$742.10