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	$133.66	8.623%	$145.1855	$145.19	$145.20	$145.20
Purchase #2	$85.64	4.223%	$89.2566	$89.26	$89.25	$89.30
Purchase #3	$155.30	11.602%	$173.3179	$173.32	$173.30	$173.30
Purchase #4	$235.32	4.682%	$246.3377	$246.34	$246.35	$246.30
Purchase #5	$68.75	5.630%	$72.6206	$72.62	$72.60	$72.60
Purchase #6	$207.55	10.325%	$228.9795	$228.98	$229.00	$229.00
Purchase #7	$54.74	13.826%	$62.3084	$62.31	$62.30	$62.30
7 purchase totals =	$940.96		$1,018.0062	$1,018.02	$1,018.00	$1,018.00