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	$231.45	5.782%	$244.8324	$244.83	$244.85	$244.80
Purchase #2	$53.28	11.817%	$59.5761	$59.58	$59.60	$59.60
Purchase #3	$65.29	11.315%	$72.6776	$72.68	$72.70	$72.70
Purchase #4	$134.28	11.406%	$149.596	$149.60	$149.60	$149.60
Purchase #5	$244.92	6.800%	$261.5746	$261.57	$261.55	$261.60
Purchase #6	$15.83	10.492%	$17.4909	$17.49	$17.50	$17.50
Purchase #7	$212.98	5.513%	$224.7216	$224.72	$224.70	$224.70
7 purchase totals =	$958.03		$1,030.4692	$1,030.47	$1,030.50	$1,030.50