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	$91.64	9.384%	$100.2395	$100.24	$100.25	$100.20
Purchase #2	$65.84	4.718%	$68.9463	$68.95	$68.95	$68.90
Purchase #3	$56.40	5.526%	$59.5167	$59.52	$59.50	$59.50
Purchase #4	$116.40	3.434%	$120.3972	$120.40	$120.40	$120.40
Purchase #5	$36.52	13.555%	$41.4703	$41.47	$41.45	$41.50
Purchase #6	$31.76	4.576%	$33.2133	$33.21	$33.20	$33.20
Purchase #7	$130.27	10.706%	$144.2167	$144.22	$144.20	$144.20
7 purchase totals =	$528.83		$568.0000	$568.01	$567.95	$567.90