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	$52.53	4.635%	$54.9648	$54.96	$54.95	$55.00
Purchase #2	$66.82	9.401%	$73.1017	$73.10	$73.10	$73.10
Purchase #3	$132.41	10.588%	$146.4296	$146.43	$146.45	$146.40
Purchase #4	$203.50	6.641%	$217.0144	$217.01	$217.00	$217.00
Purchase #5	$41.41	12.492%	$46.5829	$46.58	$46.60	$46.60
Purchase #6	$123.73	11.284%	$137.6917	$137.69	$137.70	$137.70
Purchase #7	$191.94	4.592%	$200.7539	$200.75	$200.75	$200.80
7 purchase totals =	$812.34		$876.5390	$876.52	$876.55	$876.60