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	$56.48	11.314%	$62.8701	$62.87	$62.85	$62.90
Purchase #2	$95.71	9.700%	$104.9939	$104.99	$105.00	$105.00
Purchase #3	$151.40	6.237%	$160.8428	$160.84	$160.85	$160.80
Purchase #4	$125.98	13.189%	$142.5955	$142.60	$142.60	$142.60
Purchase #5	$38.66	4.673%	$40.4666	$40.47	$40.45	$40.50
Purchase #6	$76.48	9.136%	$83.4672	$83.47	$83.45	$83.50
Purchase #7	$166.30	4.439%	$173.6821	$173.68	$173.70	$173.70
7 purchase totals =	$711.01		$768.9182	$768.92	$768.90	$769.00