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	$51.54	5.791%	$54.5247	$54.52	$54.50	$54.50
Purchase #2	$59.39	4.392%	$61.9984	$62.00	$62.00	$62.00
Purchase #3	$241.94	6.196%	$256.9306	$256.93	$256.95	$256.90
Purchase #4	$185.59	12.328%	$208.4695	$208.47	$208.45	$208.50
Purchase #5	$160.74	13.186%	$181.9352	$181.94	$181.95	$181.90
Purchase #6	$228.86	11.319%	$254.7647	$254.76	$254.75	$254.80
Purchase #7	$168.26	13.297%	$190.6335	$190.63	$190.65	$190.60
7 purchase totals =	$1,096.32		$1,209.2566	$1,209.25	$1,209.25	$1,209.20