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	$103.82	10.254%	$114.4657	$114.47	$114.45	$114.50
Purchase #2	$154.31	7.820%	$166.377	$166.38	$166.40	$166.40
Purchase #3	$163.51	11.619%	$182.5082	$182.51	$182.50	$182.50
Purchase #4	$34.49	12.422%	$38.7743	$38.77	$38.75	$38.80
Purchase #5	$143.63	4.725%	$150.4165	$150.42	$150.40	$150.40
Purchase #6	$63.99	10.735%	$70.8593	$70.86	$70.85	$70.90
Purchase #7	$90.51	10.783%	$100.2697	$100.27	$100.25	$100.30
7 purchase totals =	$754.26		$823.6707	$823.68	$823.60	$823.80