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	$152.50	8.128%	$164.8952	$164.90	$164.90	$164.90
Purchase #2	$46.54	10.155%	$51.2661	$51.27	$51.25	$51.30
Purchase #3	$132.83	12.677%	$149.6689	$149.67	$149.65	$149.70
Purchase #4	$37.81	10.256%	$41.6878	$41.69	$41.70	$41.70
Purchase #5	$154.31	4.680%	$161.5317	$161.53	$161.55	$161.50
Purchase #6	$110.49	7.106%	$118.3414	$118.34	$118.35	$118.30
Purchase #7	$35.81	13.144%	$40.5169	$40.52	$40.50	$40.50
7 purchase totals =	$670.29		$727.9080	$727.92	$727.90	$727.90