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	$133.49	7.593%	$143.6259	$143.63	$143.65	$143.60
Purchase #2	$70.31	11.127%	$78.1334	$78.13	$78.15	$78.10
Purchase #3	$105.50	13.228%	$119.4555	$119.46	$119.45	$119.50
Purchase #4	$115.94	7.243%	$124.3375	$124.34	$124.35	$124.30
Purchase #5	$239.85	8.492%	$260.2181	$260.22	$260.20	$260.20
Purchase #6	$164.52	3.701%	$170.6089	$170.61	$170.60	$170.60
Purchase #7	$250.65	12.855%	$282.8711	$282.87	$282.85	$282.90
7 purchase totals =	$1,080.26		$1,179.2504	$1,179.26	$1,179.25	$1,179.20