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	$98.32	7.661%	$105.8523	$105.85	$105.85	$105.90
Purchase #2	$230.29	13.413%	$261.1788	$261.18	$261.20	$261.20
Purchase #3	$100.48	5.204%	$105.709	$105.71	$105.70	$105.70
Purchase #4	$156.56	6.717%	$167.0761	$167.08	$167.10	$167.10
Purchase #5	$31.55	12.336%	$35.442	$35.44	$35.45	$35.40
Purchase #6	$43.77	12.108%	$49.0697	$49.07	$49.05	$49.10
Purchase #7	$11.41	10.405%	$12.5972	$12.60	$12.60	$12.60
7 purchase totals =	$672.38		$736.9251	$736.93	$736.95	$737.00