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	$181.57	10.280%	$200.2354	$200.24	$200.25	$200.20
Purchase #2	$73.52	6.140%	$78.0341	$78.03	$78.05	$78.00
Purchase #3	$77.69	5.855%	$82.2387	$82.24	$82.25	$82.20
Purchase #4	$202.38	10.866%	$224.3706	$224.37	$224.35	$224.40
Purchase #5	$148.87	3.286%	$153.7619	$153.76	$153.75	$153.80
Purchase #6	$87.29	9.476%	$95.5616	$95.56	$95.55	$95.60
Purchase #7	$87.95	13.780%	$100.0695	$100.07	$100.05	$100.10
7 purchase totals =	$859.27		$934.2718	$934.27	$934.25	$934.30