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	$212.65	3.341%	$219.7546	$219.75	$219.75	$219.80
Purchase #2	$248.89	3.203%	$256.8619	$256.86	$256.85	$256.90
Purchase #3	$54.77	12.295%	$61.504	$61.50	$61.50	$61.50
Purchase #4	$50.80	10.339%	$56.0522	$56.05	$56.05	$56.10
Purchase #5	$124.95	13.860%	$142.2681	$142.27	$142.25	$142.30
Purchase #6	$177.99	9.281%	$194.5093	$194.51	$194.50	$194.50
Purchase #7	$37.57	11.800%	$42.0033	$42.00	$42.00	$42.00
7 purchase totals =	$907.62		$972.9534	$972.94	$972.90	$973.10