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	$162.60	13.264%	$184.1673	$184.17	$184.15	$184.20
Purchase #2	$142.70	8.500%	$154.8295	$154.83	$154.85	$154.80
Purchase #3	$125.66	5.633%	$132.7384	$132.74	$132.75	$132.70
Purchase #4	$122.95	9.729%	$134.9118	$134.91	$134.90	$134.90
Purchase #5	$111.87	13.639%	$127.1279	$127.13	$127.15	$127.10
Purchase #6	$82.37	8.369%	$89.2635	$89.26	$89.25	$89.30
Purchase #7	$65.86	9.253%	$71.954	$71.95	$71.95	$72.00
7 purchase totals =	$814.01		$894.9924	$894.99	$895.00	$895.00