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	$239.82	6.264%	$254.8423	$254.84	$254.85	$254.80
Purchase #2	$228.43	5.145%	$240.1827	$240.18	$240.20	$240.20
Purchase #3	$129.91	12.493%	$146.1397	$146.14	$146.15	$146.10
Purchase #4	$74.28	11.554%	$82.8623	$82.86	$82.85	$82.90
Purchase #5	$121.25	3.170%	$125.0936	$125.09	$125.10	$125.10
Purchase #6	$109.97	5.801%	$116.3494	$116.35	$116.35	$116.30
Purchase #7	$85.96	4.367%	$89.7139	$89.71	$89.70	$89.70
7 purchase totals =	$989.62		$1,055.1839	$1,055.17	$1,055.20	$1,055.10