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	$191.85	5.455%	$202.3154	$202.32	$202.30	$202.30
Purchase #2	$185.27	7.840%	$199.7952	$199.80	$199.80	$199.80
Purchase #3	$17.41	8.553%	$18.8991	$18.90	$18.90	$18.90
Purchase #4	$151.60	11.434%	$168.9339	$168.93	$168.95	$168.90
Purchase #5	$76.54	11.831%	$85.5954	$85.60	$85.60	$85.60
Purchase #6	$70.31	11.235%	$78.2093	$78.21	$78.20	$78.20
Purchase #7	$132.81	8.671%	$144.326	$144.33	$144.35	$144.30
7 purchase totals =	$825.79		$898.0743	$898.09	$898.10	$898.00