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	$141.56	8.696%	$153.8701	$153.87	$153.85	$153.90
Purchase #2	$48.78	5.478%	$51.4522	$51.45	$51.45	$51.50
Purchase #3	$238.44	13.868%	$271.5069	$271.51	$271.50	$271.50
Purchase #4	$80.82	8.339%	$87.5596	$87.56	$87.55	$87.60
Purchase #5	$100.60	8.457%	$109.1077	$109.11	$109.10	$109.10
Purchase #6	$195.54	13.582%	$222.0982	$222.10	$222.10	$222.10
Purchase #7	$110.42	5.618%	$116.6234	$116.62	$116.60	$116.60
7 purchase totals =	$916.16		$1,012.2181	$1,012.22	$1,012.15	$1,012.30