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	$131.83	8.849%	$143.4956	$143.50	$143.50	$143.50
Purchase #2	$143.37	5.338%	$151.0231	$151.02	$151.00	$151.00
Purchase #3	$235.99	11.680%	$263.5536	$263.55	$263.55	$263.60
Purchase #4	$100.83	4.119%	$104.9832	$104.98	$105.00	$105.00
Purchase #5	$103.62	5.815%	$109.6455	$109.65	$109.65	$109.60
Purchase #6	$116.85	13.252%	$132.335	$132.34	$132.35	$132.30
Purchase #7	$224.74	12.716%	$253.3179	$253.32	$253.30	$253.30
7 purchase totals =	$1,057.23		$1,158.3539	$1,158.36	$1,158.35	$1,158.30