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	$231.57	13.565%	$262.9825	$262.98	$263.00	$263.00
Purchase #2	$214.51	12.620%	$241.5812	$241.58	$241.60	$241.60
Purchase #3	$59.30	10.616%	$65.5953	$65.60	$65.60	$65.60
Purchase #4	$207.53	8.573%	$225.3215	$225.32	$225.30	$225.30
Purchase #5	$162.46	11.786%	$181.6075	$181.61	$181.60	$181.60
Purchase #6	$54.98	11.733%	$61.4308	$61.43	$61.45	$61.40
Purchase #7	$243.78	8.254%	$263.9016	$263.90	$263.90	$263.90
7 purchase totals =	$1,174.13		$1,302.4204	$1,302.42	$1,302.45	$1,302.40