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	$179.77	7.471%	$193.2006	$193.20	$193.20	$193.20
Purchase #2	$123.89	11.248%	$137.8251	$137.83	$137.85	$137.80
Purchase #3	$48.86	5.184%	$51.3929	$51.39	$51.40	$51.40
Purchase #4	$230.28	8.724%	$250.3696	$250.37	$250.35	$250.40
Purchase #5	$120.76	4.732%	$126.4744	$126.47	$126.45	$126.50
Purchase #6	$174.88	11.844%	$195.5928	$195.59	$195.60	$195.60
Purchase #7	$172.56	10.127%	$190.0352	$190.04	$190.05	$190.00
7 purchase totals =	$1,051.00		$1,144.8906	$1,144.89	$1,144.90	$1,144.90