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	$118.40	7.452%	$127.2232	$127.22	$127.20	$127.20
Purchase #2	$54.88	4.668%	$57.4418	$57.44	$57.45	$57.40
Purchase #3	$93.37	9.857%	$102.5735	$102.57	$102.55	$102.60
Purchase #4	$59.66	11.613%	$66.5883	$66.59	$66.60	$66.60
Purchase #5	$119.73	9.783%	$131.4432	$131.44	$131.45	$131.40
Purchase #6	$118.74	13.401%	$134.6523	$134.65	$134.65	$134.70
Purchase #7	$11.43	13.714%	$12.9975	$13.00	$13.00	$13.00
7 purchase totals =	$576.21		$632.9198	$632.91	$632.90	$632.90