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	$5.32	9.306%	$5.8151	$5.82	$5.80	$5.80
Purchase #2	$161.61	8.646%	$175.5828	$175.58	$175.60	$175.60
Purchase #3	$70.93	10.364%	$78.2812	$78.28	$78.30	$78.30
Purchase #4	$171.53	4.186%	$178.7102	$178.71	$178.70	$178.70
Purchase #5	$153.90	5.564%	$162.463	$162.46	$162.45	$162.50
Purchase #6	$238.50	5.434%	$251.4601	$251.46	$251.45	$251.50
Purchase #7	$132.34	12.388%	$148.7343	$148.73	$148.75	$148.70
7 purchase totals =	$934.13		$1,001.0467	$1,001.04	$1,001.05	$1,001.10