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	$74.70	9.231%	$81.5956	$81.60	$81.60	$81.60
Purchase #2	$136.50	4.867%	$143.1435	$143.14	$143.15	$143.10
Purchase #3	$140.56	7.706%	$151.3916	$151.39	$151.40	$151.40
Purchase #4	$56.53	10.620%	$62.5335	$62.53	$62.55	$62.50
Purchase #5	$213.65	11.589%	$238.4099	$238.41	$238.40	$238.40
Purchase #6	$117.30	8.103%	$126.8048	$126.80	$126.80	$126.80
Purchase #7	$250.60	5.385%	$264.0948	$264.09	$264.10	$264.10
7 purchase totals =	$989.84		$1,067.9737	$1,067.96	$1,068.00	$1,067.90