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	$53.75	10.761%	$59.534	$59.53	$59.55	$59.50
Purchase #2	$214.45	10.862%	$237.7436	$237.74	$237.75	$237.70
Purchase #3	$56.68	4.559%	$59.264	$59.26	$59.25	$59.30
Purchase #4	$129.50	5.557%	$136.6963	$136.70	$136.70	$136.70
Purchase #5	$62.28	13.381%	$70.6137	$70.61	$70.60	$70.60
Purchase #6	$127.45	10.746%	$141.1458	$141.15	$141.15	$141.10
Purchase #7	$17.56	13.473%	$19.9259	$19.93	$19.95	$19.90
7 purchase totals =	$661.67		$724.9233	$724.92	$724.95	$724.80