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	$134.62	10.521%	$148.7834	$148.78	$148.80	$148.80
Purchase #2	$130.59	10.188%	$143.8945	$143.89	$143.90	$143.90
Purchase #3	$62.91	7.322%	$67.5163	$67.52	$67.50	$67.50
Purchase #4	$100.67	12.671%	$113.4259	$113.43	$113.45	$113.40
Purchase #5	$95.31	9.286%	$104.1605	$104.16	$104.15	$104.20
Purchase #6	$46.46	13.758%	$52.852	$52.85	$52.85	$52.90
Purchase #7	$240.82	12.667%	$271.3247	$271.32	$271.30	$271.30
7 purchase totals =	$811.38		$901.9573	$901.95	$901.95	$902.00