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	$97.65	11.421%	$108.8026	$108.80	$108.80	$108.80
Purchase #2	$144.60	9.351%	$158.1215	$158.12	$158.10	$158.10
Purchase #3	$130.29	12.745%	$146.8955	$146.90	$146.90	$146.90
Purchase #4	$112.93	6.108%	$119.8278	$119.83	$119.85	$119.80
Purchase #5	$223.84	7.368%	$240.3325	$240.33	$240.35	$240.30
Purchase #6	$138.72	6.792%	$148.1419	$148.14	$148.15	$148.10
Purchase #7	$83.59	5.103%	$87.8556	$87.86	$87.85	$87.90
7 purchase totals =	$931.62		$1,009.9774	$1,009.98	$1,010.00	$1,009.90