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	$75.90	9.465%	$83.0839	$83.08	$83.10	$83.10
Purchase #2	$164.36	8.396%	$178.1597	$178.16	$178.15	$178.20
Purchase #3	$221.29	7.776%	$238.4975	$238.50	$238.50	$238.50
Purchase #4	$129.70	8.278%	$140.4366	$140.44	$140.45	$140.40
Purchase #5	$151.94	8.215%	$164.4219	$164.42	$164.40	$164.40
Purchase #6	$99.88	5.159%	$105.0328	$105.03	$105.05	$105.00
Purchase #7	$99.29	7.333%	$106.5709	$106.57	$106.55	$106.60
7 purchase totals =	$942.36		$1,016.2033	$1,016.20	$1,016.20	$1,016.20