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	$200.85	12.776%	$226.5106	$226.51	$226.50	$226.50
Purchase #2	$45.95	5.472%	$48.4644	$48.46	$48.45	$48.50
Purchase #3	$163.31	10.175%	$179.9268	$179.93	$179.95	$179.90
Purchase #4	$63.30	13.414%	$71.7911	$71.79	$71.80	$71.80
Purchase #5	$108.74	13.845%	$123.7951	$123.80	$123.80	$123.80
Purchase #6	$158.61	9.571%	$173.7906	$173.79	$173.80	$173.80
Purchase #7	$55.38	4.616%	$57.9363	$57.94	$57.95	$57.90
7 purchase totals =	$796.14		$882.2149	$882.22	$882.25	$882.20