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	$124.50	10.720%	$137.8464	$137.85	$137.85	$137.80
Purchase #2	$56.98	4.711%	$59.6643	$59.66	$59.65	$59.70
Purchase #3	$151.94	11.272%	$169.0667	$169.07	$169.05	$169.10
Purchase #4	$155.86	6.792%	$166.446	$166.45	$166.45	$166.40
Purchase #5	$99.77	4.383%	$104.1429	$104.14	$104.15	$104.10
Purchase #6	$123.72	7.463%	$132.9532	$132.95	$132.95	$133.00
Purchase #7	$224.81	5.439%	$237.0374	$237.04	$237.05	$237.00
7 purchase totals =	$937.58		$1,007.1569	$1,007.16	$1,007.15	$1,007.10