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	$32.39	3.366%	$33.4802	$33.48	$33.50	$33.50
Purchase #2	$51.73	4.728%	$54.1758	$54.18	$54.20	$54.20
Purchase #3	$153.53	12.810%	$173.1972	$173.20	$173.20	$173.20
Purchase #4	$103.80	8.325%	$112.4414	$112.44	$112.45	$112.40
Purchase #5	$32.28	6.324%	$34.3214	$34.32	$34.30	$34.30
Purchase #6	$164.54	8.644%	$178.7628	$178.76	$178.75	$178.80
Purchase #7	$191.85	4.738%	$200.9399	$200.94	$200.95	$200.90
7 purchase totals =	$730.12		$787.3187	$787.32	$787.35	$787.30