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	$126.89	13.167%	$143.5976	$143.60	$143.60	$143.60
Purchase #2	$95.95	13.768%	$109.1604	$109.16	$109.15	$109.20
Purchase #3	$127.71	12.858%	$144.131	$144.13	$144.15	$144.10
Purchase #4	$142.49	7.182%	$152.7236	$152.72	$152.70	$152.70
Purchase #5	$208.71	7.461%	$224.2819	$224.28	$224.30	$224.30
Purchase #6	$13.96	3.721%	$14.4795	$14.48	$14.50	$14.50
Purchase #7	$238.49	3.326%	$246.4222	$246.42	$246.40	$246.40
7 purchase totals =	$954.20		$1,034.7962	$1,034.79	$1,034.80	$1,034.80