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	$92.27	13.706%	$104.9165	$104.92	$104.90	$104.90
Purchase #2	$212.86	4.335%	$222.0875	$222.09	$222.10	$222.10
Purchase #3	$109.76	13.756%	$124.8586	$124.86	$124.85	$124.90
Purchase #4	$91.94	12.668%	$103.587	$103.59	$103.60	$103.60
Purchase #5	$79.44	8.162%	$85.9239	$85.92	$85.90	$85.90
Purchase #6	$215.67	4.828%	$226.0825	$226.08	$226.10	$226.10
Purchase #7	$54.94	5.307%	$57.8557	$57.86	$57.85	$57.90
7 purchase totals =	$856.88		$925.3117	$925.32	$925.30	$925.40