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	$206.61	13.660%	$234.8329	$234.83	$234.85	$234.80
Purchase #2	$214.47	6.432%	$228.2647	$228.26	$228.25	$228.30
Purchase #3	$178.31	4.267%	$185.9185	$185.92	$185.90	$185.90
Purchase #4	$52.79	12.455%	$59.365	$59.37	$59.35	$59.40
Purchase #5	$44.59	4.639%	$46.6585	$46.66	$46.65	$46.70
Purchase #6	$189.70	12.212%	$212.8662	$212.87	$212.85	$212.90
Purchase #7	$139.25	5.347%	$146.6957	$146.70	$146.70	$146.70
7 purchase totals =	$1,025.72		$1,114.6015	$1,114.61	$1,114.55	$1,114.70