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	$90.65	5.403%	$95.5478	$95.55	$95.55	$95.50
Purchase #2	$134.30	6.618%	$143.188	$143.19	$143.20	$143.20
Purchase #3	$139.63	8.121%	$150.9694	$150.97	$150.95	$151.00
Purchase #4	$12.38	6.487%	$13.1831	$13.18	$13.20	$13.20
Purchase #5	$64.64	11.871%	$72.3134	$72.31	$72.30	$72.30
Purchase #6	$116.93	8.241%	$126.5662	$126.57	$126.55	$126.60
Purchase #7	$99.60	11.581%	$111.1347	$111.13	$111.15	$111.10
7 purchase totals =	$658.13		$712.9026	$712.90	$712.90	$712.90