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	$39.57	8.859%	$43.0755	$43.08	$43.10	$43.10
Purchase #2	$56.73	8.719%	$61.6763	$61.68	$61.70	$61.70
Purchase #3	$156.78	4.733%	$164.2004	$164.20	$164.20	$164.20
Purchase #4	$180.31	5.568%	$190.3497	$190.35	$190.35	$190.30
Purchase #5	$182.84	3.275%	$188.828	$188.83	$188.85	$188.80
Purchase #6	$96.96	7.725%	$104.4502	$104.45	$104.45	$104.50
Purchase #7	$190.89	13.526%	$216.7098	$216.71	$216.70	$216.70
7 purchase totals =	$904.08		$969.2899	$969.30	$969.35	$969.30