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	$141.82	5.820%	$150.0739	$150.07	$150.05	$150.10
Purchase #2	$98.98	4.526%	$103.4598	$103.46	$103.45	$103.50
Purchase #3	$192.45	3.231%	$198.6681	$198.67	$198.65	$198.70
Purchase #4	$132.86	13.552%	$150.8652	$150.87	$150.85	$150.90
Purchase #5	$223.64	11.606%	$249.5957	$249.60	$249.60	$249.60
Purchase #6	$179.38	11.788%	$200.5253	$200.53	$200.55	$200.50
Purchase #7	$85.89	7.363%	$92.2141	$92.21	$92.20	$92.20
7 purchase totals =	$1,055.02		$1,145.4021	$1,145.41	$1,145.35	$1,145.50