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	$116.50	9.528%	$127.6001	$127.60	$127.60	$127.60
Purchase #2	$211.76	9.123%	$231.0789	$231.08	$231.10	$231.10
Purchase #3	$120.99	3.689%	$125.4533	$125.45	$125.45	$125.50
Purchase #4	$36.81	7.221%	$39.4681	$39.47	$39.45	$39.50
Purchase #5	$233.94	7.505%	$251.4972	$251.50	$251.50	$251.50
Purchase #6	$9.36	10.456%	$10.3387	$10.34	$10.35	$10.30
Purchase #7	$80.50	12.690%	$90.7155	$90.72	$90.70	$90.70
7 purchase totals =	$809.86		$876.1518	$876.16	$876.15	$876.20