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	$178.29	5.118%	$187.4149	$187.41	$187.40	$187.40
Purchase #2	$57.60	3.636%	$59.6943	$59.69	$59.70	$59.70
Purchase #3	$19.87	9.325%	$21.7229	$21.72	$21.70	$21.70
Purchase #4	$63.72	12.162%	$71.4696	$71.47	$71.45	$71.50
Purchase #5	$51.43	10.398%	$56.7777	$56.78	$56.80	$56.80
Purchase #6	$134.70	7.719%	$145.0975	$145.10	$145.10	$145.10
Purchase #7	$195.90	13.814%	$222.9616	$222.96	$222.95	$223.00
7 purchase totals =	$701.51		$765.1385	$765.13	$765.10	$765.20