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	$64.86	10.790%	$71.8584	$71.86	$71.85	$71.90
Purchase #2	$116.47	13.853%	$132.6046	$132.60	$132.60	$132.60
Purchase #3	$241.32	4.630%	$252.4931	$252.49	$252.50	$252.50
Purchase #4	$17.48	9.407%	$19.1243	$19.12	$19.10	$19.10
Purchase #5	$170.27	11.828%	$190.4095	$190.41	$190.40	$190.40
Purchase #6	$152.50	13.854%	$173.6274	$173.63	$173.65	$173.60
Purchase #7	$199.42	5.560%	$210.5078	$210.51	$210.50	$210.50
7 purchase totals =	$962.32		$1,050.6251	$1,050.62	$1,050.60	$1,050.60