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	$225.51	8.511%	$244.7032	$244.70	$244.70	$244.70
Purchase #2	$34.89	9.129%	$38.0751	$38.08	$38.10	$38.10
Purchase #3	$179.94	9.270%	$196.6204	$196.62	$196.60	$196.60
Purchase #4	$64.86	9.156%	$70.7986	$70.80	$70.80	$70.80
Purchase #5	$48.45	13.289%	$54.8885	$54.89	$54.90	$54.90
Purchase #6	$222.31	8.738%	$241.7354	$241.74	$241.75	$241.70
Purchase #7	$100.53	4.269%	$104.8216	$104.82	$104.80	$104.80
7 purchase totals =	$876.49		$951.6428	$951.65	$951.65	$951.60