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	$119.47	11.178%	$132.8244	$132.82	$132.80	$132.80
Purchase #2	$145.48	9.514%	$159.321	$159.32	$159.30	$159.30
Purchase #3	$87.67	13.665%	$99.6501	$99.65	$99.65	$99.70
Purchase #4	$51.32	5.484%	$54.1344	$54.13	$54.15	$54.10
Purchase #5	$32.32	3.134%	$33.3329	$33.33	$33.35	$33.30
Purchase #6	$226.93	5.107%	$238.5193	$238.52	$238.50	$238.50
Purchase #7	$210.62	8.234%	$227.9625	$227.96	$227.95	$228.00
7 purchase totals =	$873.81		$945.7446	$945.73	$945.70	$945.70