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	$116.36	12.761%	$131.2087	$131.21	$131.20	$131.20
Purchase #2	$50.26	8.566%	$54.5653	$54.57	$54.55	$54.60
Purchase #3	$123.38	3.609%	$127.8328	$127.83	$127.85	$127.80
Purchase #4	$101.32	10.167%	$111.6212	$111.62	$111.60	$111.60
Purchase #5	$31.54	9.110%	$34.4133	$34.41	$34.40	$34.40
Purchase #6	$87.35	12.360%	$98.1465	$98.15	$98.15	$98.10
Purchase #7	$143.90	5.253%	$151.4591	$151.46	$151.45	$151.50
7 purchase totals =	$654.11		$709.2469	$709.25	$709.20	$709.20