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	$59.75	6.403%	$63.5758	$63.58	$63.60	$63.60
Purchase #2	$90.82	8.109%	$98.1846	$98.18	$98.20	$98.20
Purchase #3	$129.29	12.576%	$145.5495	$145.55	$145.55	$145.50
Purchase #4	$168.74	3.206%	$174.1498	$174.15	$174.15	$174.10
Purchase #5	$218.49	4.770%	$228.912	$228.91	$228.90	$228.90
Purchase #6	$33.87	11.151%	$37.6468	$37.65	$37.65	$37.60
Purchase #7	$17.58	13.823%	$20.0101	$20.01	$20.00	$20.00
7 purchase totals =	$718.54		$768.0286	$768.03	$768.05	$767.90