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	$101.36	9.587%	$111.0774	$111.08	$111.10	$111.10
Purchase #2	$217.72	4.652%	$227.8483	$227.85	$227.85	$227.80
Purchase #3	$86.74	9.594%	$95.0618	$95.06	$95.05	$95.10
Purchase #4	$198.63	9.470%	$217.4403	$217.44	$217.45	$217.40
Purchase #5	$40.97	3.246%	$42.2999	$42.30	$42.30	$42.30
Purchase #6	$111.94	12.372%	$125.7892	$125.79	$125.80	$125.80
Purchase #7	$133.53	11.504%	$148.8913	$148.89	$148.90	$148.90
7 purchase totals =	$890.89		$968.4082	$968.41	$968.45	$968.40