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	$153.51	7.376%	$164.8329	$164.83	$164.85	$164.80
Purchase #2	$148.72	10.603%	$164.4888	$164.49	$164.50	$164.50
Purchase #3	$30.73	8.296%	$33.2794	$33.28	$33.30	$33.30
Purchase #4	$164.32	12.821%	$185.3875	$185.39	$185.40	$185.40
Purchase #5	$118.30	13.490%	$134.2587	$134.26	$134.25	$134.30
Purchase #6	$92.66	13.517%	$105.1849	$105.18	$105.20	$105.20
Purchase #7	$43.90	9.501%	$48.0709	$48.07	$48.05	$48.10
7 purchase totals =	$752.14		$835.5031	$835.50	$835.55	$835.60