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	$187.37	6.698%	$199.92	$199.92	$199.90	$199.90
Purchase #2	$71.64	9.636%	$78.5432	$78.54	$78.55	$78.50
Purchase #3	$194.51	6.520%	$207.1921	$207.19	$207.20	$207.20
Purchase #4	$61.58	11.406%	$68.6038	$68.60	$68.60	$68.60
Purchase #5	$93.72	10.809%	$103.8502	$103.85	$103.85	$103.90
Purchase #6	$166.30	12.778%	$187.5498	$187.55	$187.55	$187.50
Purchase #7	$41.64	6.538%	$44.3624	$44.36	$44.35	$44.40
7 purchase totals =	$816.76		$890.0215	$890.01	$890.00	$890.00