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	$79.32	7.743%	$85.4617	$85.46	$85.45	$85.50
Purchase #2	$41.60	4.255%	$43.3701	$43.37	$43.35	$43.40
Purchase #3	$133.72	4.665%	$139.958	$139.96	$139.95	$140.00
Purchase #4	$127.42	11.763%	$142.4084	$142.41	$142.40	$142.40
Purchase #5	$230.58	5.356%	$242.9299	$242.93	$242.95	$242.90
Purchase #6	$121.97	13.638%	$138.6043	$138.60	$138.60	$138.60
Purchase #7	$105.51	4.629%	$110.3941	$110.39	$110.40	$110.40
7 purchase totals =	$840.12		$903.1265	$903.12	$903.10	$903.20