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	$243.93	4.791%	$255.6167	$255.62	$255.60	$255.60
Purchase #2	$133.65	13.540%	$151.7462	$151.75	$151.75	$151.70
Purchase #3	$77.78	7.691%	$83.7621	$83.76	$83.75	$83.80
Purchase #4	$123.96	13.298%	$140.4442	$140.44	$140.45	$140.40
Purchase #5	$98.79	12.784%	$111.4193	$111.42	$111.40	$111.40
Purchase #6	$239.80	6.871%	$256.2767	$256.28	$256.30	$256.30
Purchase #7	$145.52	13.165%	$164.6777	$164.68	$164.70	$164.70
7 purchase totals =	$1,063.43		$1,163.9429	$1,163.95	$1,163.95	$1,163.90