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	$248.42	5.564%	$262.2421	$262.24	$262.25	$262.20
Purchase #2	$165.96	4.225%	$172.9718	$172.97	$172.95	$173.00
Purchase #3	$89.54	11.112%	$99.4897	$99.49	$99.50	$99.50
Purchase #4	$172.68	11.741%	$192.9544	$192.95	$192.95	$193.00
Purchase #5	$121.35	8.719%	$131.9305	$131.93	$131.95	$131.90
Purchase #6	$54.33	13.218%	$61.5113	$61.51	$61.50	$61.50
Purchase #7	$117.25	9.367%	$128.2328	$128.23	$128.25	$128.20
7 purchase totals =	$969.53		$1,049.3326	$1,049.32	$1,049.35	$1,049.30