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	$133.71	6.798%	$142.7996	$142.80	$142.80	$142.80
Purchase #2	$27.59	3.380%	$28.5225	$28.52	$28.50	$28.50
Purchase #3	$78.86	8.394%	$85.4795	$85.48	$85.50	$85.50
Purchase #4	$195.28	6.303%	$207.5885	$207.59	$207.60	$207.60
Purchase #5	$106.69	4.491%	$111.4814	$111.48	$111.50	$111.50
Purchase #6	$190.35	3.579%	$197.1626	$197.16	$197.15	$197.20
Purchase #7	$167.51	3.268%	$172.9842	$172.98	$173.00	$173.00
7 purchase totals =	$899.99		$946.0183	$946.01	$946.05	$946.10