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	$43.77	8.508%	$47.494	$47.49	$47.50	$47.50
Purchase #2	$84.58	7.105%	$90.5894	$90.59	$90.60	$90.60
Purchase #3	$177.34	5.781%	$187.592	$187.59	$187.60	$187.60
Purchase #4	$185.77	7.406%	$199.5281	$199.53	$199.55	$199.50
Purchase #5	$220.98	5.454%	$233.0322	$233.03	$233.05	$233.00
Purchase #6	$106.92	4.218%	$111.4299	$111.43	$111.45	$111.40
Purchase #7	$12.74	3.539%	$13.1909	$13.19	$13.20	$13.20
7 purchase totals =	$832.10		$882.8565	$882.85	$882.95	$882.80