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	$87.47	5.166%	$91.9887	$91.99	$92.00	$92.00
Purchase #2	$246.54	9.336%	$269.557	$269.56	$269.55	$269.60
Purchase #3	$20.59	8.710%	$22.3834	$22.38	$22.40	$22.40
Purchase #4	$65.33	9.452%	$71.505	$71.51	$71.50	$71.50
Purchase #5	$59.57	10.583%	$65.8743	$65.87	$65.85	$65.90
Purchase #6	$139.87	13.153%	$158.2671	$158.27	$158.25	$158.30
Purchase #7	$34.25	12.478%	$38.5237	$38.52	$38.50	$38.50
7 purchase totals =	$653.62		$718.0992	$718.10	$718.05	$718.20